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SBI3U Plants: Anatomy, Growth and Functions Tissue Systems Plant Anatomy Description 1. Meristematic Tissue Growth - Undifferentiated cells that undergo mitosis Apical Meristems – tips of the plant stem shoots and root Cambium – increase the girth of a plant 2 types: Vascular cambium (phloem in dicots) & Cork cambium (produces cork in woody stem) 2. Dermal Tissue Protection - Protects the plant from disease, injury and water loss Trichomes – hair extensions decrease water loss from evaporation Root hairs – increase surface area which increases water absorption 3. Vascular Tissue Transport Xylem – transports water through specialized cells called tracheids (not living) – water moves in only one direction: from roots to leaves Phloem – transports food through specialized cells called sieve tube cells (living) – food moves in both directions in these cells 4. Ground Tissue Storage and support - Parenchyma: many functions: photosynthesis, support, storage of food and water - in roots, stems, leaves, fruit - Collenchyma: thick, flexible cell walls – support - Sclerencyma: thick, rigid walls – support Plants consists of (1) A. root – below ground, & (2) shoot – above ground: B. stems & C. leaves Plant Organ A. Root Function - Structure Absorb minerals and water from soil Transport minerals and water to stem for distribution Anchor and support the plant in soil Storage of nutrients (carbohydrates) - Protective end called a root cap Epidermis layer (outer layer) is one cell thick Epidermis may have root hairs that help absorb water and minerals by increasing the surface area of the root Cortex stores starch molecules (carbohydrates made in leaves) Vascular cylinder (inner layer) contains the plant’s conducting tissues for transport (xylem & phloem) B. Stem - Transport water and minerals to leaves Transport sugar to and from leaves Support the plant Connect leaves, roots and flowers Storage of food - - Contain vascular bundles (xylem, phloem & associated tissues) either in a ring (dicot) or scattered (monocot) - xylem located closer to the centre - phloem towards the outside - between the xylem & phloem is a thin layer called the vascular cambium Pith is the centre of the stem Cortex is the outside of the stem C. Leaves - Photosynthesis in green plants (carbohydrate/food production) 6 CO2(g) + 6 H2O(l) C6H12O6(s) + 6 O2(g) - - - - Network of veins that conduct sugar and water (continuation of vascular bundles from the stem) Cuticle – waxy covering that provides water resistance, protection and reduces water loss Mesophyll cells – cells of the leaf - Palisade layer – upper layer; very condensed; primary role is photosynthesis - Spongy layer – lower layer; has many air spaces; primary role is gas exchange Stomata - openings in the leaf that control the passage of gases and allow water vapour to escape - transpiration – loss of water vapour - Surrounded by guard cells (kidney shaped cells) which control the opening and closing of the stomata. If water enters guard cells (high water concentration), they swell thus opening the stomata. Adapted Plant Structures Specialized for their Environment Xerophytes – Desert Plants ** try to reduce water loss ** Deep roots – to absorb water from deep underground Rolled leaves – encloses stomata to reduce transpiration Leaves with spines – minimize surface area Reduced number of stomata - reduce transpiration & also close stomata during midday (evaporation highest) Thick waxy cuticle - reduce evaporation from leaf Succulent tissues & thick cortex – increased water storage Cactus Hydrophytes – Water Plants ** lots of water, need to float for maximum light ** Thick spongy mesophyll – large air spaces to allow leaves to float Large number of stomata, mostly open Stomata on upper surface of floating leaves, none on submerged leaves Thin cuticle - leaves do not dry out Large flat leaves for floatation Reduced roots – water diffuses into leaves Water lily Plant Plan : Root & Shoot (Stem & Leaves) Nodes: points on the stem where leaves are attached Internodes: intervals between the nodes Leaf axil: angle between the leaf and stem where buds usually grow Leaf Arrangement on Stem Types of Plants Woody Plants Herbaceous Plants - those that live for a number of years and survive winter - contain tough, hard tissue commonly called wood e.g. trees, shrubs (lilac) - grow thicker over time; each year vascular cambium grows layers of new xylem & phloem Bark: outer part of woody stem; protective tissue consisting of phloem & cork tissue Sapwood: younger xylem, conducts water & minerals Heartwood: older xylem that fills with resins, oils and complex compounds - stems not woody and not very supportive - green and usually soft - do not survive winter and are regrown each year e.g. buttercup SBI3U Plants: Anatomy, Growth and Functions Major Plant Groups All plants are eukaryotic, multicellular and perform photosynthesis. Adaptations to living on land include: i. Protection from drying out ii. Transport of water iii. System of support to lift plant into the air and the sunlight Group Bryophyta Filicinophyta Coniferophyta (Tracheophytes) Angiospermatophyta Other Name Mosses Ferns Gymnosperms Description Nonvascular plants Seedless vascular plants Vascular plants with naked seeds Transport System No vascular system Angiosperms (flowering plants) Vascular plants with enclosed seeds within flowers * most abundant and diversified group * Extensive vascular system Male gametes in pollen grain Specialized flowers pollinated by animals Seeds in fruit Reproduction Characteristics Size Example Seed - Plant embryo Small vascular system (xylem & phloem) Male gametes are free Male gametes are free swimming sperm swimming sperm Extensive vascular system Male gametes in pollen grain Spores (no seeds or flowers) No true leaves nor roots Spores (no seeds or flowers) Leafy fonds and small roots Naked seeds in cones All small in size Moderate in size Various sizes (large) Mosses, liverworts, hornworts Ferns Cone bearing plants Specialized leaves (needles) and roots Specialized leaves and roots Flowers Various sizes (large) Flowering plants with fruit Consists of i. Seed coat ii. Embryo (epicotyl, hypocotyl, radicle) iii. Endosperm iv. Cotyledon (seed leaf) Comparison of Types of Angiosperms: Based on Structure of Seeds Monocot Scientific Name Dicot Monocotyledoneae Dicotyledoneae ~ 50 000 species ~ 200 000 species Root Fibrous root Tap root Stem Scattered vascular bundles Leaves Flower Parts Parallel venation Narrow leaves Petals in multiples of 3s Vascular bundles in rings Herbaceous vs. Woody Netted venation Broad leaves Petals in multiples of 4s or 5s Seed Leaves 1 cotyledon 2 cotyledons Nourishment of Embryo in seed Example Endosperm nourishs embryo Cotyledons store nutrients that nourish the embryo Broad leaf plants, fruit trees, most vegetable plants Grasses, grains, rushes, bulrushes, lilies, palms, bananas, orchids SBI3U Plants: Anatomy, Growth and Functions Plant Nutrition History Aristotle Jean Baptiste van Helmont Stephen Hales - soil provided substance for plant growth - plant grow mainly from water added for growth - plants were mainly nourished by the air Plants do extract essential nutrients from soil - Soil nutrients only contribute a small part to the overall mass of the plant - 80-85% of a herbaceous plant in water o Water can be considered a plant nutrient because the hydrogen and some of the oxygen that make up water (H2O) is incorporated into organic molecules o 90% of water is transpired o Primary function of water is acting as a solvent o Functions in cell elongation, and plant form (turgid) - Majority of plant mass is derived from CO2 - After removing the water from a plant, 95% of the mass is organic and 5% is minerals - Many organic molecules contain nitrogen, sulphur and phosphorus which are relatively abundant in plants - To an extent, the minerals found in a plant reflect the composition of the soil Essential Elements 1. If required for a plant to grow from a seed and complete the life cycle producing another generation, a nutrient is considered essential. 2. If the plant is unable to produce the nutrient or element itself, it is considered essential. There are 16 essential plant nutrients Macronutrient – needed in large quantities 1. Oxygen (45.0%) 2. Carbon (45.0%) 3. Hydrogen (6.0%) 4. Nitrogen (1.5%) 5. Potassium (1.0%) 6. Calcium (0.5%) 7. Magnesium (0.2%) 8. Phosphorus (0.2%) 9. Sulphur (0.1%) Micronutrient – needed in trace amounts 10. Chlorine (0.01%) 11. Iron (0.01%) 12. Boron (0.002%) 13. Manganese (0.005%) 14. Zinc (0.002%) 15. Copper (0.0006%) 16. Molybdenum (0.00001%) SBI3U Plants: Anatomy, Growth and Functions Plant Life Cycle Types and Durations of Life Cycles Life Cycle: germination to seed production 1. Annuals - Plants whose entire life cycle occurs within one growing season - Peas, beans, tomatoes… 2. Biennials - Plants that do not produce seeds until the growing season after germination - Beets, carrots, celery, cabbage… 3. Perennials - Live from year to year and are either woody or herbaceous - The above ground portion of the herbaceous plant dies back at the end of each growing season, but persists underground Alternation of Generations The life cycles of plants consist of two generations that alternate between a haploid stage and a diploid stage. A. Diploid Stage = Sporophyte - produced by the fusion of two haploid gametes - sporophyte plants produce haploid spores by meiosis (gametes produced by meiosis) B. Haploid Stage = Gametophyte - produce haploid gametes through mitosis - has a male and female component Immature body (multicellular) Adult diploid body (multicellular) with reproductive organs Zygote 2n (single cell) Fertilization Diploid = Sporophyte ---------------------------------------------------------------------------------------------Haploid = Gametophyte Meiosis Spore n (single cell) Male Gamete (single cell) Female Gamete (single cell) Adult haploid body (multicellular) with reproductive organs