Chapter 23 Notes Roots Stems Leaves I. Specialized tissue in plants - effective way to ensure the plant s survival A. Seed plant structure 1. Roots - a. Absorbs water and dissolves nutrients b. anchors plant to the ground 2. Stems - support system and transport system 3. Leaves - Photosynthetic system 4. Tissue system - three a. dermal tissue analogous to the skin b. vascular tissue - transport water and nutrients
2- c. ground tissue all other tissues in the plant 5. Meristematic tissue - found only where growth takes place - tips of shoot and roots B. Meristematic tissue 1. only tissue that produces new cells by mitosis 2. apical meristem - undifferentiated cells that divide to produce growth C. Dermal tissue - outer covering of a plant 1. epidermal cells - dermal cells usually one layer thick
2. cuticle - waxy layer protects against water lose 3- D. Vascular tissue - specialized tissue that transports water and nutrients up, down and laterally through the plant 1. Xylem - up - tracheids and vessel elements form hollow tubes through which water can flow. 2. Phloem - down - sieve tubes and companion cells allows water to flow down and laterally through the plant 3. Ground tissue - three types of tissue
4- a. Parenchyma - function in storage and photosynthesis b. Collenchyma - strong and flexible - supports the plant c. Sclerenchyma - thick, strong and tough - also supports the plant Where in the plant are each of these found? Ans. Parenchyma - leaves Collenchyma - stems and roots Sclerenchyma - roots and stems II. Roots - surface area of roots is much larger than the plant it supports A. Types of roots - two types
5-1. taproots - thick, main root - carrot - dicots 2. fibrous roots - thin - extensive - grass - monocots B. Root structure and growth 1. root hairs - epidermis increases surface area for absorption 2. cortex - spongy layer 3. endodermis - encloses the vascular cylinder 4. vascular cylinder - phloem and xylem 5. root cap - protects root as it grows Trace and label Fig 23-7 p. 585
6- C. Root functions 1. uptake of nutrient and water 2. transport takes place in two ways a. Symplast pathway - active transport of minerals through cell walls b. Apoplast pathway - movement of water by diffusion between cells 3. Casparian strip - waterproof strip around 4 sides of a cell (cell has six sides) - controls water flow into the vascular bundle Trace and label p. 587 fig 23-9
7-4. Root pressure - water and nutrients are forced up the plant III. Stems - vary greatly in size and shape A. Stem structure and function - two 1. hold leaves up in the sunlight 2. transport substances to leaves B. Nodes and internodes 1. nodes - attachment of leaves to stems 2. internodes - space between nodes C. Buds - undeveloped tissue where new stems and leaves may develop
8- D. Monocot and dicot stems Trace and label 590 Fig 23-12 1. monocot stem - vascular bundle scattered 2. dicot stem vascular bundle arranged in a ring forming a pith E. primary growth of stems - occurs at the ends of the plant F. Secondary growth - plant increases in with to support tallness 1. vascular cambium and cork cambium - responsible for lateral growth - girth 2. formation of vascular cambium - between phloem and xylem Trace and label p. 591 fig 23-14
9-3. formation of growth rings - layers of xylem (wood) a. growth is slowed in colder months, faster in warmer months b. alternation of light and dark rings = growth rings 4. formation of bark = expansion of phloem, cork and cork cambium 5. heart wood = old dead xylem near the center of the stem - does not conduct water or nutrients 6. sapwood - surrounds heartwood and functions in transport Trace and label p. 593 fig 23-15
10- G. Adaptations of stems 1. tuber - upright, underground stem - potato 2. rhizome - horizontal underground stem - new shoots can form - ginger and strawberries 3. storage stems - cactus IV. Leaves - main organ of photosynthesis A. Leaf structure 1. blades - thin, flat, green 2. petiole - attachment to stem B. Leaf function - carries out photosynthesis 1. mesophyll - packed with chloroplasts
11- a. Palisade - column shape near top of leaf b. spongy mesophyll - loosely packed cells with air spaces Trace and label p. 596 fig. 23-18 2. Guard cells and stroma a. controls water loss and gas exchange in and out of the leaf. b. located at the bottom of the leaf c. hot and dry - stomata is closed d. cool and wet stomata open Trace and label p. 597 fig 23-19
12- C. Adaptations of leaves 1. pitcher plant - carniferous lives in nutrient poor soils - digests insects 2. cactus - leaves are thorns not photosynthetic 3. rock plant - hot/dry conditions few stomata 4. pine - narrow, thin, green reduces water loss V. Transport in plants A. water transport 1. capillarity - water rises in tubes 2. root pressure - negative pressure causes water to enter roots
13-3. transpiration pull - action of the sun that pulls water out of plants - evaporation B. Nutrient transport - phloem tissue 1. function of phloem a. movement of sugars to leaves, stems or fruits b. in cold climates sugar is stored in roots 2. Movement from source to sink - pressure flow a. increase in pressure because of movement of sugars b. this change in concentration causes movement in both directions in the phloem c. source cell - photosynthetic products moved into phloem
14- d. sink cell - sugars are lower in concentration Trace and label p. 602 fig 23-24