Chapter 23: Plant StructuresRoots, Stems, Leaves

Higher Level Vascular Plants1. Gymnosperms (cone-bearing)/ “naked seeds”- 1st seed plants- Reduced gametophytes- Depend on wind-pollination2. Angiosperms (flowering plants)- 90% of all living species- Greatly reduced gametophytes - Depends on self/ cross-pollination- Double fertilization (zygote; endosperm)- 2 classes: monocots & dicots

Plant Tissues1. DERMAL outermost layer of cells (protect)

- consist of single layer of epidermal cells- ex: cork cells, root hair cells, guard cells

2. VASCULAR plant’s bloodsteam- ex: xylem & phloem

3. GROUND cells that lie b/t dermal & vascular - makes up bulk of plants - parenchyma makes up most of ground ex: can store food (roots)/ palisade mesophyll cells photosynthesis- collenchyma & sclerenchyma support

A. 4 MAJOR PLANT ORGANS (ANGIOSPERMS)

1. LEAF PHOTOSYNTHESIS2. 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 PHLOEM2. WATER & MINERALS XYLEM3. GASES4. 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 FLOWERCOMPANION 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 BY GUARD CELLS

WATER EVAPORATION- TRANSPIRATIONDIFFUSION OF CO2 & H2O IN AND OUT

4. WASTES ALL CELLS DIFFUSION – GAS WASTES THRU LEAF STOMA;SOME WASTES EXCRETED BY ROOT SYSTEM

Phloem CellsLIVING CELLS!!!1. Sieve tube elements (STE) (main ones) cells walls have small holes/ food & sugars carried in watery stream2. Companion cells support STE and aids in movement of substances in/ out of cell

Xylem CellsDEAD CELLS!1. Tracheids long,

narrow tubes w/ walls impermeable to H20

2. Vessel Elements (VE) much wider, continuous tubes thru which H2O can move freely

LEAF ANATOMY CROSS SECTION

STOMA & GUARD CELLS

• WHEN LIGHT IS PRESENT, PHOTOSYNTHESIS IS GOING ON IN GUARD CELLS

• GUARD CELLS BECOME HYPERTONICTO SURRONDING CELLS AND TAKE IN H2O

• THEY BECOME TURGID (FIRM), WHICH OPENS THE STOMA.

• WHEN NO LIGHT, NO PHOTOSYNTHESIS

• GUARD CELLS COLLAPSE(FLACID), CLOSE STOMA***VIEW OF BOTTOM OF LEAF- LOWER EPIDERMIS

Epidermal cells*No chloroplast

*Chloroplast

3. COHESION-TENSION THEORY

• FACTORS RELATED TO XYLEM TRANSPORT1. TRANSPIRATION LOSS OF WATER FROM LEAF DUE TO EVAPORATION (DUE TO CO2 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 H2O TO SIDES OF XYLEM CELLS (RESULTS IN CAPILLARY ACTION)

4. ROOT PRESSURE FORCE EXERTED FROM ROOTS AS A RESULT OF H2O 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 (H2O ENTERS

CELLS)

*** A CONTINUOUS COLUMN OF H2O IS PRODUCED THROUGHOUT PLANT DUE TO THESE PHYSICAL FORCES WORKING AT THE SAME TIME

• ROOT HAIRS INCREASE SURFACE AREA FOR H2O ABSORPTION. - H2O IS PUSHED BY THE ROOTS, PULLED BY THE LEAVES

MERISTEMS zones of actively dividing cells

1. Apical meristems located at tips of roots and shoots (stems)- Primary growth (increase in length)- found in mono- & dicots

2. Lateral meristems located near the perphery of plants (usu in cylinder)- Secondary growth (increase in girth)a. Vacular cambium- produces secondary xylem & phloemb. Cork cambium- produces cells of outer bark

Root Cap cover at tip of root/ protects apical meristem as root pushes thru soil (primary growth)

H2O proof, prevents backflow of H2O out of vas cylinder into root cortex

MONOCOT STEMS MONOCOT PLANTS:1. ONE COTYLEDON (CORN,

GRASSES, SUGAR CANE, BAMBOO)

2. LACK PERMANENT CAMBIUM (2NDARY GROWTH ABSENT)- HERBACEOUS--> NONWOODY, GREEN & FLEXIBLE STEMS

3. SCATTERED VASCULAR BUNDLES

4. PARALLEL VEINS (LEAF)5. FIBROUS ROOT (BRANCHING)6. FLOWER PARTS IN 3’S7. STEM VASCULAR BUNDLES

SCATTERED

*** “MONKEY FACE” VASCULAR BUNDLES

support

pith & cortex

supporting tissue

DICOT STEMS

• DICOT PLANTS1. TWO COTYLEDONS (BEAN)2. PERMANENT CAMBIUM

(2NDARY GROWTH- WOODY)

3. VASCULAR BUNDLES ARRANGED IN CIRCLE AROUND CAMBIUM

4. NETTED VEINS (LEAF)5. TAP ROOT (LIKE CARROT)6. FLOWER PARTS IN 4 OR 5’S

(pith)

DICOT & MONOCOT STEMS

DICOT ROOT

Dicot Root

MONOCOT ROOT

D. MOVEMENT OF ORGANIC NUTRIENTS (PHLOEM)

• PRESSURE-FLOW OR BULK-FLOW HYPOTHESIS1. PLANT NUTRIENTS MOVE FROM AN AREA OF GREATER TO LESSER CONCENTRATION OF THAT NUTRIENTLEAF:GLUCOSE SUCROSE (PGAL) (STORAGE)

***SINK cell where sugars are used/ stored (roots, stems, flowers)

***SOURCE cells that produce sugars (leaf)

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 CELL RESPIRATION

B) FLOWERS CONSUMES GLUCOSE & C) ROOTS CONVERT IT TO ATP

PRESSURE-FLOW OR BULK-FLOW HYPOTHESIS