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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