PLANT FORM AND FUNCTION

YOU MUST KNOW…• THE FUNCTION OF XYLEM AND

PHLOEM TISSUE• THE SPECIFIC FUNCTIONS OF

TRACHEIDS, VESSELS, SIEVE-TUBE ELEMENTS, AND COMPANION CELLS

• THE CORRELATION BETWEEN PRIMARY GROWTH AND APICAL MERISTEMS VERSUS SECONDARY GROWTH AND LATERAL MERISTEMS

CONCEPT 35.1• THE PLANT BODY HAS A

HIERARCHY OF ORGANS, TISSUES, AND CELLS

• ROOT SYSTEM – ANCHORS THE PLANT, ABSORBS WATER AND MINERALS, AND OFTEN STORES SUGARS AND STARCHES

• FIBROUS ROOTS – THIN ROOTS THAT ARE SPREAD JUST BELOW THE SOIL’S SURFACE (MONOCOTS)

• TAPROOTS – ONE THICK, VERTICAL ROOT WITH MANY LATERAL ROOTS COMING OUT FROM IT (DICOTS)

• ROOT HAIRS – INCREASE THE SURFACE AREA MAKING EFFICIENT ABSORPTION OF WATER AND MINERALS POSSIBLE

• MYCORRHIZAE – SYMBIOTIC RELATIONSHIP WITH FUNGI AT THE TIPS OF THE ROOTS, ASSIST IN THE ABSORPTION PROCESS

• SHOOT SYSTEM CONSISTS OF• STEM – FUNCTION TO DISPLAY LEAVES• TERMINAL BUD – LOCATED AT THE TOP END

OF THE STEM WHERE GROWTH USUALLY OCCURS

• APICAL DOMINANCE - THE TERMINAL BUD PROHIBITS THE GROWTH OF THE AXILLARY BUDS. IT CONCENTRATES THE GROWTH OF THE PLANT UPWARD TOWARD LIGHT

• AXILLARY BUDS – LOCATED IN THE V FORMED BETWEEN THE LEAF AND THE STEM, FORM LATERAL SHOOTS

• LEAVES – MAIN PHOTOSYNTHETIC ORGAN

3 PLANT ORGAN TISSUES• DERMAL TISSUE – CLOSELY PACKED CELLS

THAT PROTECTS PLANT AGAINST WATER LOSS AND INVASION OF PATHOGENS

• VASCULAR TISSUE – TRANSPORTS MATERIALS BETWEEN ROOTS AND SHOOTS

XYLEM – TRANSPORTS WATER AND MINERAL UP FROM THE ROOTS

PHLOEM – TRANSPORTS FOOD FROM THE LEAVES TO OTHER PARTS OF PLANT

• GROUND TISSUE – BETWEEN THE DERMAL AND VASCULAR TISSUE. MAKES UP MOST OF THE BODY OF THE PLANT.

DIFFERENTIATED CELLS

XYLEM – MOST ARE DEAD CELLS2 TYPES OF CELLS1. TRACHEIDS – LONG THIN WALLS

STRENGTHENED WITH LIGNIN, WATER MOVES FROM CELL TO CELL THROUGH THE PITS IN IT

2. VESSELS – FOUND MAINLY IN ANGIOSPERMS, HAVE PITS AND PERFORATED END WALLS FOR MOST EFFICIENT WATER MOVEMENT

DIFFERENTIATED CELLSPHLOEM – LIVE CELLS – CONDUCT SUGAR

AND OTHER ORGANIC COMPOUNDS

- 2 TYPES

1. SIEVE TUBES – CHAINS OF CELLS THAT ARE HIGHLY MODIFIED FOR TRANSPORT, LACKING A NUCLEUS, RIBOSOMES, AND A CENTRAL VACUOLE

2. COMPANION CELLS – PROVIDE MOLECULAR NEEDS OF SIEVE, ARE CONNECTED TO THE SIEVE BY PLASMODESMATA

GROUND TISSUE – SUBDIVIDED INTO 3 TYPES

• PARENCHYMA – MOST ABUNDANT, THROUGHT PLANT, PERFORM MOST OF THE METABOLISM (INCLUDING PHOTOSYNTHESIS)

• COLLENCHYMA – GROUPED IN CYLINDERS THAT PROVIDE FLEXIBILITY AND HELP SUPPORT GROWING PARTS OF THE PLANT (MAINLY IN STEM AND LEAVES)

• SCHLERENCHYMA – IN PARTS THAT ARE NO LONGER GROWING, IT PROTECTS SEEDS AND SUPPORTS PLANT

CONCEPT 35.2• MERISTEMS GENERATE CELLS

FOR NEW ORGANS

LIFE CYCLE• ANNUALS – LIFE CYCLE COMPLETED

IN ONE YEAR• BIENNIALS – LIFE CYCLE COMPLETED

IN TWO YEARS• PERENNIALS – LIFE CYCLE

CONTINUES FOR MANY YEAR

MERISTEMS• EMBRYONIC TISSUES RESPONSIBLE

FOR INDETERMINATE GROWTH• APICAL MERISTEM – LOCATED AT THE

TIPS OF ROOTS AND IN BUDS OF SHOOTS AND RESULTS IN GROWTH IN IS IN LENGTH (HEIGHT) (PRIMARY GROWTH)

• LATERAL MERISTEM – RESULTS IN GROWTH THAT THICKENS THE SHOOTS AND ROOTS (WIDTH) (SECONDARY GROWTH)

CONCEPT 35.3• PRIMARY GROWTH LENGTHENS

ROOTS AND SHOOTS

• ROOT CAP – PROTECTS THE MERISTEM OF THE ROOT TIP AS IT PUSHES THROUGH SOIL

• ROOT TIP – 3 ZONES OF CELLS

1. ZONE OF CELL DIVISION – INCLUDES ROOT APICAL MERISTEM, CELLS ARE ACTIVELY DIVIDING TO MAKE NEW CELLS

2. ZONE OF ELONGATION – CELLS ABSORB H2O AND ELONGATE SIGNIFICANTLY

3. ZONE OF MATURATION – COMPLETE DIFFERENTIATION AND BECOME FUNCTIONALLY MATURE

• STOMATA – SMALL PORES ON THE UNDERSIDE OF LEAVES FLANKED BY GUARD CELLS (OPEN/CLOSE STOMATA)

• IN LEAVES, GROUND TISSUE IS SANDWICHED BETWEEN THE UPPER AND LOWER EPIDERMIS IN THE MESOPHYLL – MADE OF PARENCHYMA CELLS WHERE PHOTOSYNTHESIS OCCURS

CONCEPT 35.4• SECONDARY

GROWTH ADDS GIRTH TO STEMS AND ROOTS IN WOODY PLANTS

2 LATERAL MERISTEMS• VASCULAR CAMBIUM – PRODUCES

SECONDARY XYLEM (WOOD)• CORK CAMBIUM – PRODUCES A

TOUGH COVERING THAT REPLACE EPIDERMIS EARLY IN SECONDARY GROWTH

• BARK – OUTSIDE THE VASCULAR CAMBIUM, INCLUDES THE PHLOEM, VASCULAR AND CORK CAMBIUM

CONCEPT 35.5• GROWTH, MORPHOGENESIS, AND

DIFFERENTIATION PRODUCE THE PLANT BODY

• IT IS THE CELL EXPANSION THAT ACCOUNTS FOR THE ACTUAL INCREASE IN PLANT MASS

• MORPHOGENESIS – DEVELOPMENT OF BODY FORM AND ORGANIZATION

• PATTERN FORMATION – THE DEVELOPMENT OF SPECIFIC STRUCTURES IN SPECIFIC LOCATION

PLANT HORMONES

• ABSCISIC ACID – MAKES SURE SEENDS DON’T GERMINATE TOO EARLY, INHIBITS CELL GROWTH, AND STIMULATES THE CLOSING OF THE STOMATA

• AUXIN – LEADS TO ELONGATION OF STEMS AND PLAYS A ROLE IN PHOTOTROPISM AND GRAVITROPISM

• CYTOKININS – PROMOTE CELL DIVISION AND LEAF ENLARGEMENT, SLOWS DOWN AGING OF LEAVES

• ETHYLENE – INITIATES FRUIT RIPENING AND CAUSES FLOWERS AND LEAVES TO DROP (ASSOCIATED WITH AGE)

• GIBBERELLINS – ASSISTS IN STEM ELONGATION, INDUCES THE GROWTH OF DORMANT SEEDS, BUDS, AND FLOWERS