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Plant Anatomy Root ◦ Anchors plant in place and provides nutrition ◦ Want high SA/V Ratio Shoot (stem) ◦ Consists of stems, leaves, and flowers ◦ Leaves attached at nodes ◦ Internodes: areas between nodes Basic Plant Anatomy Roots anchor plant in soil, absorb minerals & water, & store food 1 ◦ fibrous roots (1) mat of thin roots that spread out monocots ◦ tap roots (2) 1 large vertical root Accompanied by less-prominent lateral roots Nutrient storage organ (carrots) dicots ◦ Adventitious roots Arise above ground from points along the stem Roots 2 shoots (stems) ◦ nodes Internodes ◦ buds: embryonic shoots apical buds: at tip of each stem/branch ◦ Upward & outward growth Lateral buds: where leaves meet stems flower buds & flowers Shoots stolons (strawberries) tuber (potato) Modified shoots rhizome (ginger) bulb (onion) Leaves Function of leaves ◦ photosynthesis energy production C6H12O6 production ◦ gas exchange ◦ transpiration simple vs. compound tendrils (peas) spines (cacti) succulent leaves colored leaves (poinsetta) Modified leaves Stomata Stomata: openings in epidermis of leaf that allow gas exchange between the inside of the leaf and the external environment Stomates/Stoma Operated by guard cells Stomata Both systems depend on the other ◦ roots depend on sugars produced by photosynthetic leaves ◦ shoots depend on water & minerals absorbed from the soil by roots Plant Structure sugars water & minerals Dermal ◦ epidermis (“skin” of plant) ◦ single layer of tightly packed cells that covers & protects plant Ground ◦ bulk of plant tissue ◦ photosynthetic mesophyll, storage Vascular ◦ transport system in shoots & roots ◦ xylem & phloem Plant Tissues Parenchyma ◦ ◦ ◦ ◦ “typical” plant cells = least specialized Thin walls Photosynthesis, storage, & secretion tissue of leaves, stem, fruit, storage roots Collenchyma ◦ Thick but flexible cell walls ◦ Support functions Sclerenchyma ◦ Thickest walls ◦ Support functions ◦ dead at functional maturity Plant Cell Types Parenchyma cells are unspecialized, thin, flexible & carry out many metabolic functions all other cell types in plants develop from parenchyma Parenchyma Collenchyma cells have thicker primary walls & provide support help support without restraining growth remain alive in maturity Collenchyma the strings in celery stalks are collenchyma Thick, rigid cell wall ◦ lignin (wood) ◦ cannot elongate ◦ dead at maturity Cells for support ◦ xylem vessels ◦ xylem tracheids ◦ fibers rope fibers ◦ sclereids nutshells seed coats grittiness in pears Sclerenchyma vessel elements Xylem vessel element Vascular tissue move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H2O transpirational pull dead cells Structure–Function again tracheids carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells Phloem: food-conducting cells sieve tube elements & companion cells Phloem: food-conducting cells Living cells at functional maturity ◦ cell membrane, cytoplasm Structure–Function again control of diffusion ◦ lose their nucleus, ribosomes & vacuole more room for specialized transport of liquid food (sucrose) Cells ◦ sieve tubes sieve plates — end walls — have pores to facilitate flow of fluid between cells ◦ companion cells nucleated cells connected to the sieve-tube help sieve tubes Phloem dicot monocot trees & shrubs grasses & lilies collect annual rings Vascular tissue in stems phloem xylem Vascular tissue in roots: dicot xylem phloem Vascular tissue in roots: monocot Obtaining raw materials ◦ sunlight leaves = solar collectors ◦ CO2 stomates = gas exchange ◦ H2O uptake from roots ◦ nutrients uptake from roots Putting it all together
