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Plants • What are plants and why are they important to study? **Learning Objectives • What are the characteristics – special evolutionary adaptations - of plants? • What are the major structures (vascular, reproductive, tissue) of a plant and what do the structures do? • What are the major types of plants (how are the classes broken down)? • What is the difference between a monocot & dicot? • How does a plant reproduce? • Label a flowering plant and a flower and describe the function of the parts. Plant General Characteristics 1. 2. 3. 4. 5. Carry out photosynthesis (autotrophs) Produce cellulose in their cell walls Non-motile (don’t move around) Reproduce sexually and asexually Have specialized tissues and organs Botany: the study of plants Where did Plants come from? • Plants likely evolved from plant-like Protist green algae from a watery environment. • Likely evolved around first only 500-400 million years ago! • That may seem like a long time but that means plants have been around for only about the last 10% of Earth’s history. Important Plant Adaptations • Roots: Being able to absorb nutrients through the ground from long distances. • Tissue specialization: Roots, vascular tissue, seeds, cuticle, flowers, cellulose cell walls • Cuticle: Waxy coating that prevents water loss • Pollen/male & female reproductive structures: being able to reproduce on land • Endosymbiosis of chloroplasts • Masters of utilizing capillary action. What do Plants Need to Survive? • • • • Sunlight Water and Minerals Gas Exchange Movement of Water and Nutrients • Not to be cut down. Kingdom Plantae adaptations: Specialized Tissues • **Vascular tissue (like arteries and veins!) – – • • • • (UP) Xylem – transports materials up from the roots to leaves and supports the plants as “wood” after the cell dies (DOWN) Phloem – transports materials down from the leaves to roots and stem Vascular Cambium – makes more vascular tissue Parenchyma – used for storage, surrounded by vascular tissue Meristematic tissue – only tissue that produces new cells by mitosis, found on edges Cork Cambium – outer bark of trees Contains **4 Main Groups • • • • Bryophytes Seedless Vascular Plants Gymnosperms Angiosperms Mosses Ferns Conifers Flowering plants Evolution of Plants PROTISTA Bryophytes – Non Vascular Plants • Includes: mosses, liverworts, hornworts • First land plants; had to overcome obstacles – avoid drying out (desiccation) – live in moist areas – develop a means of support (roots and stems) – develop new reproductive methods – obtaining nutrition – No vascular tissue, so they are close to the ground to draw up water by the properties of water (adhesion & cohesion)! – Their reproduction also relies on the use of water! Bryophytes Moss: common Liverwort: Marchantia polymorpha Hornworts: Anthocerotophyta Moss: Splanchnum Seedless Vascular Plants • Includes: Ferns, Club mosses, Horsetails • 3 Key Adaptations – Vascular System = xylem/phloem = larger, roots, stems, and leaves. – Larger Sporophyte = better distribution of spores – Drought resistant Spores = thickened spore wall Seedless, Vascular Plants: Ferns Fern Club Moss Horsetails Tracheophytes – Vascular Plants • Gymnosperms – means “naked seed”, not protected by fruit. Can reproduce through wind or other methods on land! – Class Ginkoopsida – Gingkos; one species exists today, living fossil – Class Cycadopsida – Cycads; found in tropics – Class Pinopsida – cone bearers; 9 families contain over 300 species, evergreens: pines, spruce, hemlocks, firs What does Vasuclar Tissue mean? Means they have xylem (water) and phloem (sugar) to transport water up from the ground into the rest of the plant! Tracheophytes – Vascular Plants Angiosperms – flowering plants, produce a form of fruit! (A wall of tissue surrounding a seed.) Gives animals a tasty treat to place their offspring elsewhere. Can reproduce on land. • Two classes of angiosperms are based upon the number of Cotyledon: tiny seed leaves that store or absorb food for developing embryo. • Class Monocotyledonae – Monocots (1) • Class Dicotyledonae – Dicots (2) • Have Unique life spans. – Those who die in one season are called annuals. – Those who die in two years are called biannuals. – Those who live many years are called perennials. Plant Structure: Roots • Roots anchor plants into the ground, absorb water & minerals from the soil, protect the plant from bad bacteria/fungi, and transport these materials to the stem. • Contain xylem and phloem in the center of the root. • Root pressure – dew is an example of root pressure (forcing excess water out of the plant) • The root cap burrows through the soil and the cells are replenished by the apical meristem. • Meristem = areas of rapidly dividing cells Plant Structure: Stems • Stems can be either woody or herbaceous. • Transpiration – as water evaporates, the energy released pulls water up the stem • Vascular tissues are arranged differently in stems than leaves. – Monocots: scattered in stem – Dicots: circular pattern in stem • Xylem – transports water & minerals • Phloem – transports sugars & hormones – Portion of a plant that stores sugar is called a sink. Plant Structure: Leaves • Leaves are protected by a waxy cuticle. • Petiole – vascular tissues extending from stem to leaf (appear as veins) • Mesophyll – contain chlorophyll • Guard cells & Stomata – regulate water loss through the underside of the leaf (Transpiration) • Monocots: parallel veins • Dicots: net veined Plant Asexual Reproduction • Vegetative Reproduction – when plants form new plants from portions of their own roots, stems, or leaves • Spores – non-seed vascular plants (ferns) release spores Plant Sexual Reproduction Overview • Pollination – when pollen is deposited on stigma. • Fertilization – when pollen grain reached the ovary and fuses with the egg. • After fertilization, the seed develops food storage regions for the embryo called fruit. • Seeds are eventually dispersed using many different methods. (Wind, Animals, Water, Fruit, etc) • Remember, this is called the Alternation of Generations! • Can remain dormant until temperature and moisture cause the seed to start early growth called germination. • The systematic cultivation of plants by humans is called agriculture. How Plants Reproduce: Flowers & Flowering • Flowers are made up of four organs: (called Perfect Flower) – Petals – colorful leaf like structure around the stem. Pistil or • They attract insects and other pollinators of the flower. – Sepals –leaf-like structure around the flower stem beneath the petals. • They enclose the bud before it opens and protect the flower while it is developing. – Stamens – male part of the flower where at their tip is the anther that rests on the filament contains pollen. – Carpel– [Also called the Pistil] Female part of the flower, which contains sticky stigma where Not all sepals are green. pollen grains land and travel down Alstroemeria (a lily-like monocot) have sepals the style to the ovary and ovules. the same color as the petals. Fertilization: Seed & Fruit Production • 2 sperm fertilize the female, one the egg (1n), the other the central cell (2n) • The walls of the ovule become the protective seed coat, the central cell becomes the endosperm or food for the embryo, and the ovary wall the fruit. • Because two fertilization events take place at the same time, it is called double fertilization. • Fruits and seeds are modified for dispersal. – Shape of seed can determine type of dispersal (wind, water, animal, etc) • Seeds can stay dormant for long periods of time! Maple seed. The fruit isn’t edible but designed with a wing to float away from the tree. Plant Responses: Hormones • Hormones cause a physiological change either in growth or development. – Auxins (IAA) – stem elongation. – Gibberellins – increase rate of seed germination and allows the stem to grow taller. – Cytokinins – stimulate proteins for cell division and extends the life of the plant. – Ethylene – ripens fruits and the emergence of seeds from the soil. – Abscisic Acid – helps leaves prevent water loss by hardening certain leaf cells. Plant Responses: Tropisms • Plants respond to their environment as other organisms do. • Photoperiodism affects the timing of flower production. – Duration of light and dark periods in the day – Short-day plants, Long-day plants, day-neutral plants • Tropism – a plant’s response to an external stimulus that comes from a particular direction. • Involve growth, so they are not reversible. – Phototropism (Light) – Gravitropism (Gravity) – Thigmotropism (Touch) • Nastic movement –Does not involve growth, so are reversible. – Example: folding of a venus flytrap.