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Plant Anatomy & Physiology Root Anatomy Warm-up Grab a plant and take it out of the pot Answer the following: -How is the soil being held in place? - What can you see in the soil and on the roots? Use hand lenses or stereoscopic microscopes to observe roots closely.. -Why are the roots so hairy? Lesson Essential Question • Connect the importance of roots to the survival of a plant. Student Learning Objectives •Examine the functions of roots in plants. •Identify the parts of a root. •Differentiate the two major types of root systems. •Evaluate the health of a root system. Terms • root cap • root hairs • roots • secondary roots • taproot system • unavailable water • water-holding capacity • aeration • apical meristem • available water • epidermis • fibrous root system • napiform root • primary root What are the functions of a plant’s roots? • A plant’s health is very closely tied to its roots. • Root health is often closely linked to good soil aeration, which is the exchange of gases in the medium. • A high percentage of pores in soil provides good aeration. • When roots are weak or diseased, the whole plant has difficulties. What are the functions of a plant’s roots? • The roots need to be constantly growing in order to stay healthy. • This is one reason that a plant growing in one pot for a long time tends to become root bound. What are the functions of a plant’s roots? • Soil moisture plays a significant role in helping or hurting the root systems and involves the following: • Available water is water that can be absorbed by the plant roots. • Unavailable water is a thin film of water that binds so tightly to the medium’s particles that it cannot be used by the plants. • Water-holding capacity refers to the ability of soils to hold water. Sandy soils have low water-holding capacity, and clay soils have high water-holding capacity. What are the functions of a plant’s roots? • The roots anchor the plant to the ground and support the above ground part of the plant. • The roots store food that has been made through photosynthesis. • This food can be used later when a plant needs it to grow or survive. What are the parts of a root? • When a plant seed germinates, the first structure to emerge from the seed is a root. • This root becomes the primary root and on some plants the most important root in the whole root system. What are the parts of a root? • Other roots eventually branch out from the primary root. • These are called secondary roots. • At the tip of the root, there is an area where new cells develop, which is called the apical meristem. • The apical meristem is easily damaged and so it has a root cap over the top to protect it from damage as it grows through the large and sometimes coarse soil particles. What are the parts of a root? • The surface of the root is covered with a skin of cells called the epidermis. • This epidermis is where the water and minerals enter the root through osmosis and diffusion. • The larger the surface area of the epidermis, the better able the plant is to bring in water and minerals. What are the parts of a root? • The epidermis cells begin to elongate and grow hair-like projections. • These projections, called root hairs, greatly increase the surface area of the root and allow much more water and minerals to enter the plant. What are the two types of root systems? • Plant root systems are organized in two basic ways; both have a lot to do with primary and secondary roots. • A root system that is composed of one main primary root and many secondary roots branching off of the primary root is called a taproot system. • Many dicot plants have taproot systems. • A specialized type of taproot is called a napiform root. • Examples of napiform roots include radishes, beets, and carrots. What are the two types of root systems? • A system that has no dominant primary root but is made of many primary and secondary roots of similar size is called a fibrous root system. • Monocot plants typically have fibrous root systems. What are the two types of root systems? What does a healthy root system look like? • A healthy root system is white or nearly white in color and smells fresh. • If roots are black, brown, or dark orange and smell rotten or sour, the root system is having some problems. • Although a plant growing outside has a majority of roots in only the top two feet of soil, a plant in a pot should have its roots evenly dispersed throughout the soil in the pot. What does a healthy root system look like? • Watering a plant properly is one of the most important ways to keep the root system healthy. • Proper watering for most plants involves growing the plants in pots with proper drainage holes in the bottom of the pot. • The pot is soaked with water until it is dripping out of the drainage holes. • This encourages roots to grow through the entire pot. What does a healthy root system look like? • The plant’s soil is usually allowed to dry slightly before watering again. • If plants have adequate drainage, over-watering of plants is not a matter of how much water, but of how often watering occurs. Activity • Identify the structures of roots • Lab worksheet Exit Ticket •1. What are the functions of a plant’s roots? •2. What are the parts of a root? •3. What are the two types of root systems? •4. What does a healthy root system look like? Plant Anatomy & Physiology Stem Anatomy Warm-Up 1. From the branch, what can you tell about the tree that it was growing on? 2. How many structures on the stem can you identify? Lesson Essential Question • Interpret the function of a stem and its importance to the plant. Student Learning Objectives •Describe the functions of a stem. •Recognize the external structures of a stem. •Analyze the internal structures of a stem. •Distinguish between the different types of specialized stems. Terms • apical meristem • bud • bud scale scar • bud scales • bulb • cambium • corm • cortex • heartwood • internode • lateral bud • leaf scar • lenticels • node • phloem • rhizome • sapwood • stolon • terminal bud • translocation • tuber • vascular cambium • xylem What are the functions of a stem? • Stems have many important jobs in a plant. • Stems are responsible for the size and shape of a plant. • Some stems are made of wood, and some are herbaceous or soft. What are the functions of a stem? • The following are four functions of stems. • Stems support the leaves. They hold the leaves in the most efficient position to collect sunlight. • Stems move water, minerals, and manufactured food throughout the whole plant. The movement of materials through vascular tissues is known as translocation. What are the functions of a stem? • Stems that are green in color help produce food through photosynthesis. While this is not usually the primary food production, it can be quite important in plants with no leaves or very small leaves. • Stems store food that has been manufactured by the plant. What are some of the structures on the outside of a stem? • Many structures on the stem are useful to us in identifying plants. • The following are some external structures on a stem. • The growing point at the tip of the stem, called the apical meristem, is contained inside of the bud at the end of the stem, which is called the terminal bud. • The apical meristem is the same type of structure that the tip of the root has and is responsible for growth in the length of the plant. What are some of the structures on the outside of a stem? • The leaf is attached to the stem at the node. • The area between leaves is called an internode. • At the node, just above where the leaf is attached, there is always a side bud called the lateral bud. • On the outside of both terminal and lateral buds are small protective structures called bud scales. What are some of the structures on the outside of a stem? • When the leaf falls off of the stem, it leaves behind a small scar just below the lateral bud. • This scar is called the leaf scar. • When the buds sprout each spring, the bud scales fall off, leaving behind a ring of scars called the bud scale scar. • The distance between bud scale scars represents one year’s growth of the stem. • Lenticels are small spots on the stem that allow it to exchange gases with its environment. What are some of the structures on the outside of a stem? What are some of the structures inside a stem? • Inside of the stem, there are tissues used to transport materials throughout the plant. • Stem tissues are organized in one of the following ways. • The important vascular tissues are either found in small bundles scattered throughout the stem or arranged in rings or a ring of vascular bundles, which are located in the cortex. What are some of the structures inside a stem? • The first way, scattered bundles, is found in monocots. • The second way, in rings, is found in dicots. • There are three important types of tissue found inside of the stem. What are some of the structures inside a stem? • The xylem is tissue that conducts the water and minerals throughout the plant. • The xylem is made of tube-like cells that grow together to conduct liquids. • Xylem tends to be found closer to the center of the stem. What are some of the structures inside a stem? • The phloem is tissue that conducts food that is produced in the leaf to the rest of the plant. • Phloem cells also form tubes. • Phloem is generally found toward the outside of the stem. What are some of the structures inside a stem? • Vascular cambium is tissue that is responsible for the production of new xylem and phloem. • It is responsible for growth in girth of the stem and is generally found between the xylem and the phloem. What are some of the structures inside a stem? • The darker wood to the center of the tree is called the heartwood. • The xylem cells of the heartwood have filled with gums, resins, pigments, and tannins. • They provide strength and no longer function in conducting materials. • The lighter wood circling the heartwood is called the sapwood. ―The younger sapwood actively conducts water and dissolved minerals. What are some of the structures inside a stem? • The age of a tree can be determined by counting annual growth rings. • During rapid growth, the cells of the wood are thin walled and large in diameter. • As growth slows during mid-to-late summer, the wood cells produced by the cambium become smaller and have thicker walls. • Each ring is the growth during one growing season. What are some different kinds of specialized stems? • We generally expect stems to be upright and above ground. • Some stems are modified to store food or to help the plant reproduce. • Some stems grow beneath the soil instead of above it. • The following are some types of specialized stems. What are some different kinds of specialized stems? • A bulb is a very short flattened stem that has several fleshy leaves attached to it. • Bulbs tend to be found beneath the soil. An onion is a bulb. • A corm is a spherical structure, much like a bulb. The entire structure, however, is stem as opposed to stem and leaves. A gladiolus is a corm. What are some different kinds of specialized stems? • A rhizome is a thick underground stem that lies horizontally. Hostas and Mother-in-law’s Tongue are rhizomes. • A stolon is a horizontal stem that lies above the ground. Stolons are sometimes called runners and tend to be involved with the spreading of the plant. Strawberries spread by stolon. What are some different kinds of specialized stems? • A tuber is a rhizome with a tip that is swollen with stored food. Irish potatoes are tubers. What are some different kinds of specialized stems? Exit Ticket •1. What are the functions of a stem? •2. What are some of the structures on the outside of a stem? •3. What are some of the structures inside a stem? •4. What are some different kinds of specialized stems? Plant Anatomy & Physiology Leaf Anatomy Warm-up Compare/Contrast the leaves given to you - What is similar? - What is different? - Why do you think these leaves are the same or different? Student Learning Objectives •Describe the main parts of a leaf. •Compare common vein patterns found in leaves. •Examine how a leaf is organized. •Distinguish some major types of leaves. •Differentiate major leaf arrangements. Terms • midrib • netted veins • opposite • alternate • palisade mesophyll • compound leaf • palmately compound • cuticle • palmately netted • dichotomous • parallel veins venation • petiole • epidermis • guard cells • pinnately compound • leaf blade • pinnately netted • simple leaf • leaflet • spongy mesophyll • stomata • subopposite • whorled Lesson Essential Question • Explain the importance of the leaf and the job it performs for a plant. What are the main parts of a leaf? • Leaves are the primary food-producing organs of the plant. • They are designed to efficiently collect light and use that light energy to produce food. • The main sun-collecting structure on the leaf is a large broad flat surface called the leaf blade. What are the main parts of a leaf? • The blade is held away from the stem and supported by a leaf stem called the petiole. • The petiole is not exactly like a stem, but it does have xylem and phloem so it can transport water and sugar. What are the main parts of a leaf? • Many leaves are organized with one main vein running down the middle of the blade. • This vein is called the midrib. • All of the veins, the petiole, and the midrib help position the blade in a way that it is facing the light source. What are the main parts of a leaf? What are some vein patterns found in leaves? • Veins of flowering plants are found in several patterns. • Most of these patterns can be categorized into two groups. • Monocots have leaves with parallel veins. • While the veins may not be parallel in a strict mathematical sense, none of the veins on the leaf cross. • It may look like they are fused together at the top or bottom of the blade. • Corn and grass plants are good examples of monocot leaves. What are some vein patterns found in leaves? • Dicots have veins that connect and branch from each other. • Veins in a branching pattern are called netted veins. • Some leaves with netted veins have several smaller veins branching out of a dominant midrib, which is a condition known as pinnately netted. What are some vein patterns found in leaves? • Other leaves have several dominant veins branching out from the petiole. • This condition is known as palmately netted. • A few plants have a spreading vein pattern called dichotomous venation; a gingko leaf is an example. How is a leaf organized? • A leaf is organized to collect sunlight and turn it, through photosynthesis, into food. • The leaf blade has many layers of tissue to allow this to happen. • On top of the leaf is a waxy non-cellular layer called the cuticle. • The cuticle is on the leaf to prevent water from escaping. How is a leaf organized? • The next layer on the leaf is also there for protection. • The epidermis is the skinlike layer of cells found on both the top and the bottom surface of the leaf. • The epidermis may be one or many layers thick. How is a leaf organized? • Directly beneath the upper epidermis is a layer of cells that are standing on end and packed very tightly. • These standing cells are responsible for most of the photosynthesis in the leaf and are called the palisade mesophyll. How is a leaf organized? • Located under the palisade mesophyll are loosely packed cells called the spongy mesophyll. • The spongy mesophyll forms air spaces that hold raw materials to be used and products of photosynthesis. How is a leaf organized? • The lower epidermis has holes in it for gas exchange. • The holes, stomata, can open and close. • The opening and closing is controlled by the guard cells, which surround each stoma. What are some of the major types of leaves? • Many different types of leaves exist. • Some leaves have adapted to hot, dry climates by storing water or being smaller. • Some leaves have very large blades to collect the maximum light in a shady location. What are some of the major types of leaves? • In some leaves, the blade is broken into several sections. • A leaf that has only one blade on its petiole is called a simple leaf. Most plants have simple leaves. What are some of the major types of leaves? • In some leaves, the blade is divided into three or more sections. • A leaf with multiple blades, called leaflets, is said to be a compound leaf. What are some of the major types of leaves? • There are many different kinds of compound leaves. • A palmately compound leaf has all its leaflets attached to a common point. • A pinnately compound leaf has multiple leaflets attached along a rachis or axis. What are the major leaf arrangements? • The arrangement of leaves on a stem varies from one genus to another. • Leaves are arranged along stems in one of four major ways. • When leaves and buds are arranged directly across from each other on a stem they are said to be opposite. What are the major leaf arrangements? • Leaves and buds that are spaced along a stem in an alternating fashion are termed alternate. What are the major leaf arrangements? •A third arrangement is subopposite, which refers to a condition where leaves and buds are not spaced far enough apart to be called alternate nor perfectly opposite. What are the major leaf arrangements? • When three or more leaves and buds are attached at a node, the arrangement is called whorled. Exit Ticket 1. What are the main parts of a leaf? 2. What are some vein patterns found in leaves? 3. How is a leaf organized? 4. What are some of the major types of leaves? 5. What are the major leaf arrangements? Plant Anatomy & Physiology Flower Anatomy Warm-up - What is sexual reproduction? Lesson Essential Question • What is the purpose of the flower? Student Learning Objectives •Describe the parts of a flower. •Explain the purpose of a flower. •List some different types of flowers. •Describe the difference between monocot and dicot flowers. Terms • anther • calyx • complete flower • corolla • fertilization • filament • imperfect flower • incomplete flower • ovary • perfect flower • petals • pistil • pistillate • pollen • pollination • sepals • stamen • staminate • stigma • style What are the parts of a flower? • Flowers are the most obvious part of most plants. • They are made of many intricate and important parts. • Most flowers contain both male and female parts. What are the parts of a flower? • The male part of the flower is called the stamen, which is made of the stalk-like filament that holds up the sack-like anther. • The anther contains pollen, the grain released by flowers, which contains the sperm. • Flowers that only have male parts are called staminate. What are the parts of a flower? • The female part of the flower is called the pistil. • It consists of a sticky tissue at its end called the stigma, which is receptive to pollen. • Below the stigma is a rodshaped middle part called the style and a swollen base containing eggs called the ovary. • Flowers that only have female parts are called pistillate. What are the parts of a flower? What are the parts of a flower? • Flowers also often have parts that are neither male nor female; these are the petals, usually colorful leaf-like structures that often attract animals and insects. • When all of the petals are fused together, we call them a corolla. What are the parts of a flower? • Beneath the petals are more leaf-like structures, called sepals, which are often green. The sepals support the petals and protect the flower before it opens. • When all of the sepals are fused together, we call them a calyx. What is the purpose of a flower? • The purpose of a flower is for a plant to be able to reproduce sexually. • The process of sexual reproduction in plants follows. • The first step in sexual reproduction is for the stamen to release its pollen. • The pollen is carried by animal, wind, gravity, or many other methods to the stigma of another flower. What is the purpose of a flower? • When the pollen from one flower lands on the stigma of a compatible flower, we call it pollination. • Flowers are adapted to pollinate each other in an astounding number of different ways using an equally amazing number of methods, called vectors, to help them. What is the purpose of a flower? • Once the pollen reaches the stigma, it starts to go down into the style, depositing sperm in the ovary. • When the sperm combines with the eggs in the ovary, we call it fertilization. • After the eggs have been fertilized, the ovary and surrounding tissue start to enlarge to become a fruit and the fertilized eggs become seeds. What are some different types of flowers? • Flowers come in many shapes, sizes, and colors. Not all of them have all of the structures mentioned previously. • A flower that has both male and female parts is called a perfect flower. • A flower that is missing either male or female parts is called imperfect flower. What are some different types of flowers? • If a flower has sepals, petals, pistils, and stamens, we call it a complete flower. • If a flower is missing one of those, we say it is an incomplete flower. • Imperfect flowers are always incomplete. Incomplete flowers may or may not be imperfect. How is a monocot flower different from a dicot flower? • A good way to tell the difference between a monocot and a dicot is to look closely at the flowers. • Monocots have flowers with flower parts in multiples of three. • Dicots have flowers with flower parts in multiples of four or five. Exit Ticket 1. What are the parts of a flower? 2. What is the purpose of a flower? 3. What are some different types of flowers? 4. How is a monocot flower different from a dicot flower? Plant Anatomy & Physiology Light, Temperature, Air and water effects on plant growth Interest Approach Students love to set up experiments. This is your chance to allow them to set up their own. Allow the class to have 10–15 plants. This can be done in groups or as an entire class. Tell the students they need to study the effects of light, temperature, air, and water on plants. For example, you might use four plants and put one in a bright window, one on the teacher’s desk, one in a greenhouse or under a bright light, and one in a dark closet in order to study the effects of light. Interest Approach Allow students to be creative. Within a week you will start to see some serious differences. Students can check and measure the progress of the plants at the beginning of each class as a gathering and interest activity. You may ask students to draw conclusions from their data. This can take the form of a discussion, paper, or an oral presentation. Student Learning Objectives •Examine the effect of light on plants. •Describe a plant’s temperature needs. Student Learning Objectives •Explain how the quality of air affects plants. •Determine a plant’s water needs. Terms • day neutral plant (dnp) • DIF • electromagnetic spectrum • foot candle • hardiness • humidity • long day plant (ldp) • photoperiod Terms • photoreceptor • phytochrome • plant heat-zone map • plant hardiness zone map • short day plant (sdp) • soluble salts • thermoperiod • vernalization • wilting How does light affect plants? • The sun emits a wide range of radiation. • The light we see is called visible light. • It is a small segment of all the radiant energy given off by the sun. • Visible light is what drives photosynthesis. • Some other types of radiation are X-rays, gamma rays, ultraviolet rays, microwaves, and radio waves. How does light affect plants? • The wavelengths of the different rays are measured in nanometers. • Based on their wavelengths, the rays have been placed on an electromagnetic spectrum. How does light affect plants? • Sunlight contains a complete blend of visible colors including red, orange, yellow, green, blue, and violet. • Plants need mostly the colors blue and red to activate the chlorophyll. • Other pigments collect other colors of light and pass that energy to the chlorophyll to make more sugar. How does light affect plants? • Different colors of light solicit different plant responses. • Red light promotes seed germination, seedling growth, and stem elongation. • Red wavelengths also influence flowering and anthocyanin (pigments in blue, red and purple flowers) formation. How does light affect plants? • Blue light reduces stem length, increases branching, and promotes stem strength. • Blue light improves leaf and flower color, too. • Far-red light triggers a shade avoidance response in plants when levels of blue or red light are low. • Stems stretch and become weak while leaves become thinner and wider. • Far-red light also plays a key role in breaking seed dormancy and in photoperiod responses. How does light affect plants? • Light intensity can have an impact on crops. • Intensity of light depends largely on the angle of the sun, clouds, and dust in the atmosphere. • Light intensity is greater in the summer months when the sun is higher in the sky. How does light affect plants? • Light intensity is measured in foot candles. • A foot candle is the amount of light distributed by a single candle one foot away. • A sunny, summer day provides about 10,000 foot candles of light. • The high light intensity elevates the rate of photosynthesis; as a result, the plant is able to produce more food. How does light affect plants? • Plants receiving the optimum level of light will be compact and have good leaf color. • Symptoms of lower than optimum light levels include a slower growth rate, thin leaves, small flowers, dull leaf and flower color, and etiolation or stretching. • Extended periods of cloud cover can slow crop growth and ultimately reduce yields. How does light affect plants? • Some plants are responsive to the length of time they are exposed to light. • These plants have a photoreceptor or light-sensitive pigment that absorbs light. • Phytochrome is a type of photoreceptor within plants that detects day lengths. • The length of the days or the length of the light period is known to influence different phases of plant growth, such as flowering. How does light affect plants? • Other phases are seed germination, enlargement of leaves, and development of buds. • A plant’s response to light duration is called photoperiod. How does light affect plants? • Plants can generally be separated into three groups based on the photoperiod response. • Short day plants (SDP) are plants that begin to flower when the nights are more than 12 hours long. • Long day plants (LDP) begin to flower when the nights are under 12 hours long. • Day neutral plants (DNP) are plants with a flowering response that is unaffected by the photoperiod. What temperatures are best for plants? • Plants have adapted to a wide range of temperatures. • Some plants thrive within the Arctic Circle and others can survive in the blazing sun of a desert. • Plants tend to adapt for higher temperatures with smaller leaves in lighter colors with thicker cuticles. What temperatures are best for plants? • Plants adapt to low temperatures by growing lower to the ground with short life cycles and parabolic dish-shaped flowers to collect light and heat. • Although plants can survive higher and lower extremes, plants do not really grow at temperatures below 32 degrees Fahrenheit or above 100 degrees Fahrenheit. What temperatures are best for plants? • A plant’s ability to withstand low temperatures is called its hardiness. • A plant that is very hardy can survive in a cold climate. • Hardiness is measured using the USDA plant hardiness-zone map. What temperatures are best for plants? • Each area of the country is assigned a zone number (1 to 10). • A plant proven to withstand zones 1–4 will survive the cold temperature extremes in zone 5, but a plant rated for zone 6–11 would likely die. • Hardiness zones are derived from the average coldest temperatures for the year. What temperatures are best for plants? • Heat also plays a role in the performance of plant species. • Some plants are more sensitive to heat than others. • The plant heat-zone map has been developed by the American Horticultural Society to help identify areas in which landscape plants can flourish. • The map shows 12 zones. What temperatures are best for plants? • Each zone reflects a rating of summer heat based on the average number of days above 86F. • Eighty-six degrees is a temperature at which plants are unable to process water fast enough to maintain normal functions. • Plants also experience damage to cellular proteins at temperatures above 86F. What temperatures are best for plants? What temperatures are best for plants? • The inability of a plant to absorb enough water to replace water lost through transpiration can be a problem in hot weather. • Plants that lose water faster than it can be replaced become flaccid, a condition known as wilting. • The guard cells also wilt, causing the stomata to close. • Without an exchange of gases, photosynthesis shuts down. What temperatures are best for plants? • Thermoperiod is a term used to describe a temperature requirement that produces a plant response. • Poinsettias and holiday cactus are examples of thermoperiodic plants. • A period of cool temperatures along with short days causes them to initiate flowering. What temperatures are best for plants? • For some floriculture crops, a period of cold temperature is required for flowering. • This physiological process is known as vernalization. • Bulb crops like tulips, narcissus, and Easter lilies must undergo vernalization. • A common practice is to expose bulbs to freezing or near freezing temperatures for a number of weeks to satisfy the plant’s cold requirement What temperatures are best for plants? • Greenhouse growers use temperature to control the height of plants. • They do this by managing the difference between daytime and nighttime temperatures. • The mathematical difference between the day temperature and the night temperature is called DIF. • DIF can be positive, negative, or zero. What temperatures are best for plants? • A positive DIF results when the day temperature is higher than the night temperature. • Positive DIF causes a plant to lengthen its stems. • A negative DIF occurs when the day temperature is cooler than the night temperature. • Plants grown under negative DIF conditions have limited stem elongation. • Zero DIF is a result of identical day and night temperatures. How does the quality of air affect plants? • Air contains carbon dioxide and oxygen, both of which are necessary for plant growth. • Oxygen is necessary for cellular respiration to occur in a normal manner. • Oxygen is picked up mainly by the roots of the plant. How does the quality of air affect plants? • Carbon dioxide is used for photosynthesis in very high amounts. • Carbon dioxide usually enters the plant through the leaves via the stomata. • In greenhouses, we often try to boost the level of carbon dioxide to speed up photosynthesis. How does the quality of air affect plants? • Humidity, which is water vapor in the air, affects plant growth. • The growth rate of plants increases under conditions of high humidity. • Lush, tropical forests exist, in part, because of frequent rain and high humidity. How does the quality of air affect plants? • High humidity reduces water stress of a plant so photosynthesis can function smoothly. • If the humidity is low, the dryness of the air can put stress on the plant. • This is especially true if soil moisture is inadequate and wilting occurs. • One drawback of excessive humidity is the increase of leaf and flower diseases. How does the quality of air affect plants? • Air pollution can be damaging to plants. • Dust in the air can reduce light intensity, slowing photosynthesis. • Chemical pollutants, such as sulfur dioxide and ozone, can actually kill plant cells or the entire plant. How do plants get water? • Plants receive most water through the root system. • In some situations, plants can soak up water through stems or take in water through leaves. • Watering is the most important cultural practice in horticulture. • Life processes of plants depend on water. • Photosynthesis and respiration require water. How do plants get water? • Roots are able to absorb minerals only if the minerals are dissolved in water. • Water is the carrier of materials through the xylem and phloem. • Water also comprises a large percentage of the plant cells, tissues, and organs. How do plants get water? • Water must be given to plants when needed to avoid damage to the root system. • Timing is critical. Frequent applications of water can keep a growing medium too wet. • The result may be damaged plant roots caused by the lack of good air exchange. How do plants get water? • Plants in containers should be grown in pots with drainage holes so the water can drain and allow oxygen into the root zone. • Allowing soils to become too dry between waterings may also cause root death and lower the quality of the crop. How do plants get water? • A good rule is to water plants thoroughly when they need water and wait until they need water before watering again. How do plants get water? • Water with a favorable pH range of 5.8 to 6.2 is best for most plant growth. • If the water supply has a pH outside that range, the pH can be adjusted. • A second consideration in determining water quality involves soluble salts. • Soluble salts are dissolved minerals. • Water with high levels of soluble salts is detrimental to plant growth. • Soluble salts damage roots. Review/Summary •How does light affect plants? •What temperatures are best for plants? •How does the quality of air affect plants? •How do plants get water? Plant Anatomy & Physiology Supplying nutrients Horticulture Science Lesson 22 Supplying Nutrients to Floriculture Crops Interest Approach Lay out several examples of fertilizers. Pick a flowering plant and ask the students to find the correct fertilizer for that particular plant. Ask them why they chose that fertilizer. Repeat this activity with a houseplant and a vegetable plant. Then ask the students to describe how they would use the fertilizer (e.g., mix with water, apply to the soil, spray on the leaves). Finally, ask the students to describe what is in the fertilizer that helps plants grow. Student Learning Objectives •Discuss plant nutrition. •Describe pH and how it is modified. Student Learning Objectives •Describe the components of a fertilizer. •Explain the methods of applying fertilizers to horticultural crops. Terms • chlorosis • complete fertilizer • fertilizer • fertilizer analysis • fertilizer injector systems • incomplete fertilizer • limestone • macronutrient • micronutrient Terms • nutrient deficiency • parts per million (ppm) • plant nutrition • primary macronutrients • secondary macronutrients • slow release fertilizer • soil pH • soil test • sulfur • water-soluble fertilizer What is plant nutrition? • Plants need nutrients for healthy growth and development. • Plant nutrition involves the absorption of nutrients for plant growth and is dependent on 16 essential elements, often referred to as nutrients. What is plant nutrition? • Three of the 16 elements comprise 89 percent of a plant’s tissue by dry weight: oxygen (O), hydrogen (H), and carbon (C). • They are considered to be non-fertilizer nutrients. • The plant acquires these three elements through natural processes from air and water. What is plant nutrition? Six essential elements in addition to oxygen, hydrogen, and carbon are required in greater quantity than the others; they are called macronutrients. • The macronutrients are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). • 1. Nitrogen, phosphorus, and potassium are considered primary macronutrients because they are used in complete fertilizers. • Nitrogen promotes green leafy growth. • Phosphorus encourages flowering and root growth. • Potassium provides disease resistance. What is plant nutrition? • 2. Calcium, magnesium, and sulfur are said to be secondary macronutrients because plants need them in moderate amounts. • These secondary macronutrients may or may not be used in complete fertilizers. What is plant nutrition? • The other seven essential elements, called micronutrients, are needed in small quantities. • These are sometimes called trace elements. They are boron (B), copper (Cu), chlorine (Cl), iron (Fe), manganese (Mn), molybdenum (Mo), sodium (Na), and zinc (Zn). • Six of these (boron, copper, iron, manganese, molybdenum, sodium, and zinc) are supplied to plants as fertilizers. • Chlorine is not added to fertilizers since plants obtain sufficient quantities of chlorine from the medium or from water. What is plant nutrition? A little phrase can be used to help memorize the 16 essential elements for plant growth. • It is “C. B. Hopkins Café Mighty Good Closed Monday See You Zen.” • It represents the following: Carbon (C), Boron (B), Hydrogen (Hopkins), Oxygen (HOpkins), Phosphorus (HoPkins), Potassium (HopKins), Nitrogen (HopkiNs), Sulfur (HopkinS), Calcium (Café), Iron (café), Magnesium (Mighty good), Chlorine (Closed), Manganese (Monday), Molybdenum (Morning), Copper (See you = Cu), Zinc (Zen). What is plant nutrition? • Other elements play important roles in plant growth and development. • For instance, silicon (Si) improves plant strength and disease resistance. • Nickel (Ni) is another element considered important for plant growth. What is plant nutrition? • Plants receive most of the nutrients they need from the growing media. • In order to maintain healthy plants, a grower must provide the right type and amount of nutrients to the media so the plants can absorb the nutrients and grow. • 1. A soil test can be performed to determine which nutrients are present and which nutrients are deficient or lacking. • 2. When nutrients are deficient in the soil, the plant growth is adversely affected. What is plant nutrition? • It is common for plant leaves to show symptoms of a nutrient deficiency by turning colors. • When nitrogen is deficient in the soil, a plant’s older leaves turn yellow. • Abnormal yellowing of plant leaves is a condition called chlorosis. • A plant will show purpling in the stem or leaf when phosphorus is deficient. What is pH and how is it modified? • Many times, the nutrients needed for plant growth are present in the soil, but the plants do not have access to the nutrients. • Nutrient availability is influenced by the pH of the soil. • Soil pH measures the amount of acidity or alkalinity and is based on the amount of hydrogen ions present in the soil. What is pH and how is it modified? • Soil pH can range from 1 to 14. • A pH reading of 7 is neutral. • Substances that have pH readings below 7 are acidic. • Substances with pH readings above 7 are alkaline or basic. What is pH and how is it modified? • Plants have specific pH ranges that are ideal for maximum plant growth. • Most plants grow best at a pH of 5.5 to 7 because the most nutrients are available for the plant to absorb in that range. • Some important horticultural plants (azaleas) do better in a medium that has a more acidic pH. What is pH and how is it modified? • A soil test can be performed to determine the pH of the soil, and amendments can be added to modify the pH. • Limestone is commonly added to growing medium in order to raise the pH. • Sulfur or sulfur compounds can be added to the media to lower the pH. What are the components of a fertilizer? • A fertilizer is any material added to growing medium that provides nutrients for plants. • Fertilizers vary in the components they contain, the way they are applied, and the function they serve. What are the components of a fertilizer? • When choosing a fertilizer, one should always look for the fertilizer analysis on the bag or box. • The fertilizer analysis states the percentage of primary nutrients (nitrogen, phosphate, and potash) present in the fertilizer. • The analysis is written as three numbers (i.e., 15-10-26), which represent the percent of nitrogen, phosphorus, and potash present in the fertilizer. • They are always listed in that order. What are the components of a fertilizer? • Fertilizer analysis What are the components of a fertilizer? • If a fertilizer contains all three primary nutrients, it is called a complete fertilizer. • If a fertilizer is lacking any of the three primary nutrients, it is an incomplete fertilizer. • The fertilizer analysis does not equal 100%. • The rest of the fertilizer composition consists of filler materials (necessary for the fertilizer to be applied) and possibly some micronutrients. How are fertilizers applied to horticultural crops? • Different plants have different nutrient requirements; some are heavy feeders and others are light feeders. How are fertilizers applied to horticultural crops? Plants have different nutrient requirements based on the stage of growth. • The first stage is when the plant is a young seedling or cutting. • In the second stage, vegetative or leafy growth is encouraged. How are fertilizers applied to horticultural crops? • This is followed by the flower bud initiation stage, the flower bud development stage, and the flowering stages. • Each stage calls for different rates of fertilizers. • In the vegetative stage, plants use more nitrogen, whereas the flowering stage requires less nitrogen and more phosphorus. How are fertilizers applied to horticultural crops? • Fertilizers are typically applied as water-soluble fertilizer or as slow-release fertilizers. 1. Water-soluble fertilizers dissolve completely in water and stay in solution. • The concentrations of the water-soluble fertilizers are also easily adjusted. • The fertilizer concentrate is then mixed with the water in exact proportions before irrigating plants. How are fertilizers applied to horticultural crops? • Fertilizer injector systems are standard equipment in today’s greenhouses. • With fertilizer injector systems, growers can provide exact levels of water-soluble fertilizers to a crop. How are fertilizers applied to horticultural crops? 2. Slow-release fertilizers continually discharge a small amount of nutrients into the growing media over a period of time. • They are available in two forms. • One form consists of a water-soluble fertilizer held within a plastic resin or sulfur coating and is designed to allow a small amount of fertilizer to be slowly released; they have the appearance of little round beads and are sometimes mistaken as insect eggs by the uninformed. How are fertilizers applied to horticultural crops? • The other type of slow-release fertilizer comes in a granular form. • This type releases no more than one percent of the fertilizer in a 24-hour period. How are fertilizers applied to horticultural crops? • There are a number of advantages to using fertilizer injectors. • The greenhouse plants are provided with constant liquid feeding, which is especially important with soilless media that have a low cation-exchange capacity. • The plants are fertilized when they are watered, thus reducing labor. How are fertilizers applied to horticultural crops? • All the plants of a particular crop receive the same levels of nutrients, which assists in producing a uniform crop. • In addition, adjustments to the level of nutrients in solution can be made easily. How are fertilizers applied to horticultural crops? • Nutrients in solution are measured in parts per million or PPM. • Fertilizer rates can be taken from tables in reference books or to instructions with their injector system, or growers can calculate the amount of fertilizer needed to reach a desired PPM. • In either case, it is beneficial for a grower to understand how to calculate parts per million (PPM) of fertilizer nutrients. How are fertilizers applied to horticultural crops? 1. An example problem might call for 200 PPM nitrogen. • The chosen fertilizer is calcium nitrate with an analysis of 15-0-0. • A rule of thumb in calculating PPM is that 1 ounce of anything in 100 gallons H2O equals 75 PPM. How are fertilizers applied to horticultural crops? • Problem: Wanted, 200 PPM N 15-0-0 Calcium Nitrate • Multiply the percent of the nutrient in the given fertilizer by 75. • .15 N × 75 = 11.63 PPM N (if 1 oz added to 100 gallons) 200 divided by 11.63 = 17.2 oz of fertilizer needed in 100 gallons to get 200 PPM. How are fertilizers applied to horticultural crops? • If the injector system delivers 1:100 (one gallon concentrate mixed with 99 gallons water for a total of 100 gallons), 17.2 ounces of fertilizer is needed for each gallon of concentrate. • If the tank holds 30 gallons of concentrate, 516 ounces (32.25 pounds) of fertilizer is needed to deliver 200 PPM. Review/Summary •What is plant nutrition? •What is pH and how is it modified? Review/Summary •What are the components of a fertilizer? •How are fertilizers applied to horticultural crops? Plant Anatomy & Physiology Plant Breeding Interest Approach • Ask the students to tell you what they have heard about genetically modified organisms (GMO). Make a list of these items on the board. Discuss these items briefly. Ask the students to make a copy of the list. Tell them that you will take another look at the items on this list after you have completed the unit. At that time, ask what the students know about GMOs. What items changed? Objectives • 1 Define plant breeding, and examine the history of plant domestication and improvement. • 2 Define the selection process. • 3 Define hybrid, and describe the three basic types of hybrids. • 4 Compare and contrast the four classes of commercial seed. • 5 Discuss the advantages of genetic engineering as compared to conventional plant-breeding techniques. Terms • • • • • • • breeder seed certified seed double cross foundation seed genetic engineering genotype hybrid vigor Terms • • • • • • • hybridization mass selection pedigree selection phenotype plant breeding pure line selection registered seed Terms • • • • • • selection single cross three-way cross top cross totipotent transgenic plants What is plant breeding, and what is the history of plant domestication and improvement? • I. Plant breeding is the systematic process of improving plants using scientific methods. A variety of methods are used to pollinate certain plants and to prevent the unwanted pollination of other plants. What is plant breeding, and what is the history of plant domestication and improvement? A. The goals of plant breeding vary according to the type of plant improvement desired. Plant breeding may be used to accomplish a variety of goals. 1. Gain disease resistance 2. Gain insect resistance 3. Improve environmental adaptation 4. Improve productivity 5. Make a species more suited to cultural practices 6. Obtain a more desirable product from plants What is plant breeding, and what is the history of plant domestication and improvement? B. The genotype is the genetic makeup of a plant. Plant breeders are continually looking for new plant genotypes that will produce desired results. The outward or physical appearance of a plant is the plant’s phenotype. Changes in plant genotype will most often result in a change in the plant’s phenotype. In their work to develop new plants, plant breeders often develop new plant cultivars, which are cultivated plants that have specific and distinguishable characteristics. Another important attribute of a cultivar is that plants within a cultivar will retain the characteristics of that group when reproduced. What is the selection process? • II. One of the most common methods used in plant breeding is selection, which is the process of selecting plants for breeding based on particular characteristics. Selection leads to the dominance of certain genetic traits, such as yield and quality of the crop, drought tolerance, and resistance to disease, pests, and herbicides. What is the selection process? • A. Selection for the purpose of plant breeding started with the domestication of plants by early man. However, selection has occurred without human influence. Natural selection is a process essential to evolution. With an increased knowledge of agriculture, humans introduced crop species to geographical areas outside the natural range of the plant species. What is the selection process? • 1. The key to selection is the availability of variability within species. The best performing plants are chosen, and the rest of the population is discarded or rejected. The offspring of the selected plants are grown, and the best performing offspring are chosen for the desired feature. This process is repeated over and over. In time, a uniform crop with the desired characteristics is produced. What is the selection process? • 2. Plant selection is carried out by three common methods. • a. Selection for uniform plants is known as pure-line selection. A variety developed by this method is more uniform than a variety developed by mass selection because all of the plants in such a variety have the same genotype. Instead of adding the seed from selected plants together, they are kept apart and used to perform offspring tests. What is the selection process? • b. The simplest and oldest method, known as mass selection, involves the selection of individual plants based on phenotypic performance. The bulk seed produced is used for the next generation. For hundreds of years, mass selection resulted in the improvement of corn. However, improvement of yields slowed. The problem was in the lack of control over the pollen parent. In effect, the selection is limited only to the female parent plants. What is the selection process? • c. The selection from a well-documented list of parentage is commonly known as pedigree selection. Parental lines are crossed. Each generation of selected populations that follow is subjected to selection until genetic uniformity is reached. Records are kept of the origin of the selected individuals or lines. What is a hybrid, and what are the three basic types of hybrids? • III. Hybridization is the process of breeding distinctly different species or varieties to achieve a hybrid. The goal of this procedure is to gain a superior characteristic in the offspring. Often hybrid plants exhibit a trait known as hybrid vigor, which is a condition where the offspring may have greater yield, height, disease resistance, or other traits than either of the parents. What is a hybrid, and what are the three basic types of hybrids? • A. Hybridization may be a double cross, a three-way cross, a single cross, or a top cross. • 1. A double cross is defined as the first generation of a cross between two Foundation single crosses. • 2. A three-way cross is the first generation of a cross between a Foundation single cross as one parent and an inbred line or a Foundation backcross as the other parent. What is a hybrid, and what are the three basic types of hybrids? • 3. A single cross is the first generation of a cross between two inbred lines: an inbred line and a Foundation backcross or of two Foundation backcross. • 4. A top cross is the first generation of a cross between an inbred line and an open-pollinated variety or the first generation of a cross between a single cross and an openpollinated variety. What are the four classes of commercial seed? • IV. There are four recognized classes of commercial seed. • A. Breeder seed is seed directly controlled by the originating or sponsoring plant-breeding organization. • B. Foundation seed is the progeny of Breeder or Foundation seed handled to maintain specific genetic purity and identity. What are the four classes of commercial seed? • C. Registered seed is the progeny of Breeder or Foundation seed handled to maintain satisfactory genetic purity and identity. • D. Certified seed is the progeny of Breeder, Foundation, or Registered seed handled to maintain satisfactory genetic purity and identity. What are the advantages of genetic engineering as compared to conventional plant-breeding techniques? V. Genetic engineering is the direct manipulation of an organism’s genes. Also, known as recombinant technologies, genetic engineering may involve removing, modifying, or adding genes. This process permits scientists to select and move fairly specific sections of genetic material from one living organism to another. The organisms do not have to be related, so there are an increased number of genes available for plant breeding. WHAT ARE THE ADVANTAGES OF GENETIC ENGINEERING AS COMPARED TO CONVENTIONAL PLANT-BREEDING TECHNIQUES? • A. The plants into which genes from another organism have been incorporated are called transgenic plants. To genetically modify an entire plant, the initial transfer of genetic information occurs at the single-cell level. The process is aided by the plant’s ability to grow from a singlecell, meaning the plant is totipotent. What are the advantages of genetic engineering as compared to conventional plant-breeding techniques? • B. There are advantages to genetic engineering: yields improve, money is saved because damage to the crop is lessened, and the need for applying pesticides may be reduced. Desired results can be obtained much more quickly than with traditional breeding methods. There is also greater control over which characteristics will be expressed in the offspring. What are the advantages of genetic engineering as compared to conventional plant-breeding techniques? C. Researchers have targeted a number of areas for improved performance of agronomic crops. They are developing plants that will be resistant to diseases, herbicides, insects, and viruses. Work is being done to engineer plants that will be tolerant of cold, drought, and salty soils. The nutritional properties of foods may be improved through genetic engineering. Storage properties may be improved to reduce losses to spoilage before the food can be sold. Also, the appearance of fruits and vegetables may be enhanced, resulting in increased consumer appeal. REVIEW • 1. What is plant breeding, and what is the history of plant domestication and improvement? • 2. What is the selection process? • 3. What is a hybrid, and what are the three basic types of hybrids? • 4. What are the four classes of commercial seed? • 5. What are the advantages of genetic engineering as compared to conventional plant-breeding techniques?