Chapter 23 Plant Structures Roots Stems Leaves A

Chapter 23: Plant Structures Roots, Stems, Leaves

A. 4 MAJOR PLANT ORGANS (ANGIOSPERMS) 1. LEAF PHOTOSYNTHESIS 2. STEM TRANSPORT, SUPPORT OF LEAVES & FLOWERS, STORAGE (STARCH) 3. ROOT ABSORPTION OF WATER AND MINERALS, ANCHORAGE, STORAGE, SYNTHESIS OF PROTEINS (RESPIRATION) 4. FLOWER SEXUAL REPRODUCTION (RESPIRATION)

B. TRANSPORT SYSTEM 1. ORGANIC NUTRIENTS PHLOEM 2. WATER & MINERALS XYLEM 3. GASES 4. WASTES

NUTRIENT CELLS MECHANISM RESPONSIBLE 1. ORGANIC NUTRIENTS (GLUCOSE/ SUCROSE) PHLOEM ALIVE SIEVE TUBES & COMPANION CELLS BULK-FLOW HYPOTHESIS (PRESSURE FLOW) FOLLOWS CONCENTRATION GRADIENT FROM LEAF ROOT, STEM, OR FLOWER COMPANION CELLS TRANSLOCATION 2. WATER & MINERALS XYLEM DEAD VESSEL CELLS & TRACHEIDS COHESION-TENSION THEORY (PUSH/PULL) ROOT LEAF, STEM, OR FLOWER 3. GASES LEAF STOMA CONTROLLED WATER EVAPORATIONTRANSPIRATION BY GUARD CELLS DIFFUSION OF CO 2 & H 2 O IN AND OUT 4. WASTES ALL CELLS DIFFUSION – GAS WASTES THRU LEAF STOMA; SOME WASTES EXCRETED BY ROOT SYSTEM

Xylem Cells

Phloem Cells

LEAF ANATOMY CROSS SECTION

STOMA & GUARD CELLS Epidermal cells *No chloroplast *Chloroplast ***VIEW OF BOTTOM OF LEAF- LOWER EPIDERMIS • WHEN LIGHT IS PRESENT, PHOTOSYNTHESIS IS GOING ON IN GUARD CELLS • GUARD CELLS BECOME HYPERTONIC TO SURRONDING CELLS AND TAKE IN H 2 O • THEY BECOME TURGID (FULL), WHICH OPENS THE STOMA. • WHEN NO LIGHT, NO PHOTOSYNTHESIS • GUARD CELLS COLLAPSE (FLACID), CLOSE STOMA

3. COHESION-TENSION THEORY • FACTORS RELATED TO XYLEM TRANSPORT 1. TRANSPIRATION LOSS OF WATER FROM LEAF DUE TO EVAPORATION (DUE TO CO 2 INTAKE) 2. COHESION ATTRACTION OF “LIKE” MOLECULES; WATER MOLECULES ARE POLAR (CHARGED) Hydrogen Bond

CONT. FACTORS RELATED TO XYLEM TRANSPORT 3. ADHESION ATTRACTION OF “UNLIKE” MOLECULES- ATTRACTION OF H 2 O TO SIDES OF XYLEM CELLS (RESULTS IN CAPILLARY ACTION) 4. ROOT PRESSURE FORCE EXERTED FROM ROOTS AS A RESULT OF H 2 O ABSORPTION (OSMOSIS) – ROOT CELLS ARE HYPERTONIC TO SOIL 5. OSMOSIS MOVEMENT OF WATER FROM A REGION OF GREATER TO LESSER WATER CONCENTRATION, THROUGH SEMI-PERMEABLE MEMBRANE – ROOT EPIDERMAL CELLS ARE HYPERTONIC TO SOIL (H 2 O ENTERS CELLS) *** A CONTINUOUS COLUMN OF H 2 O IS PRODUCED THROUGHOUT PLANT DUE TO THESE PHYSICAL FORCES WORKING AT THE SAME TIME

• ROOT HAIRS INCREASE SURFACE AREA FOR ABSORPTION. - H 2 O IS PUSHED BY THE ROOTS, PULLED BY THE LEAVES

MONOCOT STEMS *** “MONKEY FACE” VASCULAR BUNDLES support pith & cortex supporting tissue MONOCOT PLANTS: 1. ONE COTYLEDON (CORN, GRASSES, SUGAR CANE, BAMBOO) 2. LACK PERMANENT CAMBIUM 3. SCATTERED VASCULAR BUNDLES 4. PARALLEL VEINS (LEAF) 5. FIBROUS ROOT (BRANCHING)

DICOT STEMS (pith) • DICOT PLANTS 1. TWO COTYLEDONS (BEAN) 2. PERMANENT CAMBIUM 3. VASCULAR BUNDLES ARRANGED IN CIRCLE AROUND CAMBIUM 4. NETTED VEINS (LEAF) 5. TAP ROOT (LIKE CARROT)

DICOT & MONOCOT STEMS

DICOT ROOT

MONOCOT ROOT

D. MOVEMENT OF ORGANIC NUTRIENTS (PHLOEM) • PRESSURE-FLOW OR BULK-FLOW HYPOTHESIS 1. PLANT NUTRIENTS MOVE FROM AN AREA OF GREATER TO LESSER CONCENTRATION OF THAT NUTRIENT LEAF: GLUCOSE SUCROSE (PGAL) (STORAGE)

PRESSURE-FLOW OR BULK-FLOW HYPOTHESIS

2. LEAF REPRESENTS AREA OF HIGHER CONCENTRATION OF GLUCOSE OR SUCROSE. – GLUCOSE FLOWS THROUGH PHLOEM SIEVE TUBE CELLS FROM LEAVES TO OTHER PLANT ORGANS HAVING LOWER CONCENTRATIONS A) STEMS B) FLOWERS C) ROOTS CELL RESPIRATION CONSUMES GLUCOSE & CONVERT IT TO ATP