Chapter 24 PLANT STRUCTURE and FUNCTION

Overview of PLANT STRUCTURE Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Vegetative shoot Blade Petiole Stem Leaf Taproot Lateral roots Root system Shoot Axillary Vegetative organs are concerned with growth and nutrition Flowers, seeds, and fruits are structures involved in reproduction.

Flowering Plants: Monocots or Eudicots Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Seed Root Stem Leaf Flower Monocots Root xylem and phloem in a ring Vascular bundles scattered in stem Leaf veins form a parallel pattern Flower parts in threes and multiples of three One cotyledon in seed Eudicots Root phloem between arms of xylem Vascular bundles in a distinct ring Leaf veins form a net pattern Flower parts in fours or fives and their multiples Two cotyledons in seed 10

ROOTS Roots Generally, the root system is at least equivalent in size and extent to the shoot system Anchors plant in soil Absorbs water and minerals Produces hormones Root hairs: Projections from epidermal root hair cells Greatly increase absorptive capacity of root

Roots 1 Roots anchor plant in soil, absorb minerals & water, & store food fibrous roots (1) mat of thin roots that spread out monocots tap roots (2) 1 large vertical root also produces many small lateral, or branch roots dicots root hairs (3) increase absorptive surface area 2 3

Shoots Shoots consist of stems, leaves & buds Stems Buds nodes = points at which leaves are attached internodes = stem segments between nodes Buds growth of shoot terminal or apical bud = at tip of plant axillary bud = in nodes on stem

STEMS Support for the plant body Carries nutrients throughout plant Defense system to protect against predators and infection Few millimeters to 100 meters

LEAVES Leaves are the major part of the plant that carries on photosynthesis Foliage leaves are usually broad and thin Blade - Wide portion of foliage leaf Petiole - Stalk attaches blade to stem Leaf Axil - Axillary bud originates Tendrils - Leaves that attach to objects Bulbs - Leaves that store food

colored leaves (poinsetta) Modified leaves tendrils (peas) spines (cacti) succulent leaves colored leaves (poinsetta)

Interdependent systems Both systems depend on the other roots receive sugars & other nutrients from photosynthetic parts shoot system depends on water & minerals absorbed from the soil by roots sugars water

Putting it all together Obtaining raw materials sunlight leaves = solar collectors CO2 stomates = gas exchange H2O uptake from roots nutrients

TISSUES OF FLOWERING PLANTS Dermal “skin” of plant single layer of tightly packed cells that covers & protects plant Vascular transport materials between roots & shoots xylem & phloem Ground everything else: storage, photosynthetic bulk of plant tissue

DERMAL TISSUE Dermal Tissue Outer covering Single layer of cells consisting of Cuticle – waxy coating Hairs Guard Cells that surround stomata

Those would’ve been great names Cells of GROUND TISSUE Those would’ve been great names for my kids! Parenchyma “typical” plant cells = least specialized photosynthetic cells, storage cells tissue of leaves, stem, fruit, storage roots Collenchyma unevenly thickened primary walls = support Sclerenchyma very thick, “woody” secondary walls (lignin) = support Fibers (rope); Schlereids (grittiness, hardness of nuts, peach pit) rigid cells that can’t elongate dead at functional maturity

VASCULAR TISSUE Transports materials in roots, stems & leaves Xylem carry water & minerals up from roots tube-shaped dead cells only their walls provide a system of microscopic water pipes Phloem carry nutrients throughout plant sugars (sucrose), amino acids… tube-shaped living cells

Xylem Dead at functional maturity Cell elongated into tubes tracheids Aaaaah… Structure-Function again! Dead at functional maturity Cell elongated into tubes tracheids long, thin cells with tapered ends walls reinforced with lignin = support thinner pits in end walls allows water flow vessel elements wider, shorter, thinner walled & less tapered perforated ends walls allows free water flow from one hole to the next

Phloem Living cells at functional maturity Cells Aaaaah… Structure-Function again! Living cells at functional maturity lack nucleus, ribosomes & vacuole more room: specialized for liquid food (sucrose) transport Cells sieve tubes end walls, sieve plates, have pores to facilitate flow of fluid between cells, pump sugars companion cells nucleated cells connected to the sieve-tube Surround sieve tubes; support phloem cells

Phloem: food-conducting cells sieve tube elements & companion cells

Vascular tissue in herbaceous stems dicot trees & shrubs monocot grasses & lilies

What I should eat…. What I actually eat….

Root structure: dicot phloem xylem

Root structure: monocot