CONTROL SYSTEMS IN PLANTS

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CHAPTER 39

• CONTROL SYSTEMS IN PLANTS

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• HORMONES TO EXCITE
• A COMPOUND PRODUCED BY ONE PART OF AN ORGANISM
  THAT IS TRANSPORTED TO OTHER PARTS, WHERE IT WILL
  TRIGGER A RESPONSE IN TARGET CELLS

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• PLANT HORMONES
• GROWTH, DEVELOPMENT AND RESPONSE TO STIMULI
• CONTROL PLANT GROWTH AND DEVELOPMENT BY AFFECTING
  THE DIVISION, ELOGATION AND CELL DIFFERENTIATION
• EFFECT WILL DEPEND ON THE SITE OF ACTION OR THE
  STAGE OF PLANT GROWTH AS WELL AS THE
  CONCENTRATION OF THE HORMONE
• HORMONE SIGNAL MAY BE ENHANCED BY GENE EXPRESSION
  OR ENZYMES
• THE RELATIVE CONCENTRATION OF HORMONES MAY EFFECT
  RESPONSE AS WELL

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• CLASSES OF PLANT HORMONES
• AUXINS
• STIMULATE STEM ELONGATION, ROOT GROWTH,
  DIFFERENTIATION AND BRANCHING. FRUIT DEVELOPMENT
  AS WELL AS APICAL DOMINANCE. PHOTOTROPISM AND
  GEOTROPISM (GRAVITOTROPISM)
• SEEDS MAY ALSO SYNTHESIZE AUXINS.
• MAY ALSO INDUCE FRUIT DEVELOPMENT WITHOUT
  POLLINATION

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• CYTOKININS
• AFFECT ROOT GROWTH AND DIFFERENTIATION, STIMULATE
  GERMINATION
• DELAY SENESCENCE
• STIMULATE CELL DIVISION (CYTOKINESIS) WORK WAS
  DONE AT CSH LABS BY JOHANNES AND OVERBEEK
• COMPLIMENTED BY AUXIN CONCENTRATION

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• GIBBERILLINS
• PROMOTE SEED AND BUD GERMINATION AND LEAF GROWTH
• STIMULATE FLOWERING AND FRUIT DEVELOPMENT
• AFFECT ROOT GROWTH

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• ABSICISIC ACID (ABA)
• INHIBITS GROWTH
• CLOSE STOMATES DURING PERIODS OF WATER STRESS
• ABA/GIBBERILLIN RATIO DETERMINES IF A SEED WILL
  GERMINATE OR NOT

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• ETHYLENE
• GASEOUS HORMONE THAT DIFFUSES THROUG AIR SPACES
  BETWEEN PLANT CELLS
• PROMOTES FRUIT RIPENING
• PROMOTES OR INHIBITS GROWTH AND DEVELOPMENT OR
  ROOTS, LEAVES AND FLOWERS
• MAY OPPOSE AUXINS

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• LEAF ABSICICCION
• PROCESS OF STORING NUTRIENTS PRIOR TO LEAVES
  FALLING OFF DURING AUTUMN

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• OLIGOSACCHARIDES
• FOUND IN THE CELL WALL
• TRIGGERS A DEFENSE RESPONSE AGAINST PATHOGENS
• REGULATES GROWTH, CELL DIFFERNTIATION AND
  FLOWERING

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• BRASSINOSTEROIDS
• NEEDED IN PLANTS FOR NORMAL GROWTH AND DEVELOPMENT

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• PLANT MOVEMENT
• TROPISMS
• GROWTH RESPONSE THAT RESULTS IN THE ENTIRE PLANT
  OR PLANT ORGANS MOVING TOWARD OR AWAY FROM A
  STIMULUS
• POSITIVE TOWARDS
• NEGATIVE - AWAY

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• PHOTOTROPISM
• SHOOT TIP IS THE RESPONSE SITE
• CRYPTOCHROME (PHOTORECEPTOR) PIGMENT THAT IS
  SENSITIVE TO BLUE LIGHT. IT IS ALSO INVOLVED IN
  STOMATA OPENING
• ROOTS NEGATIVE
• SHOOTS - POSITIVE

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• GRAVITOTROPISM
• RESPONSE TO GRAVITY
• ROOTS POSITIVE
• SHOOTS NEGATIVE
• PLANTS CAN TELL UP FROM DOWN BY SPECIALIZED
  PLASTIDS THAT CONTAIN DENSE STARCH GRAINS
• STATOLITHS FOUND IN LOW POINTS OF CELLS IN
  CERTAIN CELLS OF THE ROOT CAP
• FALLING STATOLITH HYPOTHESIS
• STATOLITHS MAY ENHANCE GRAVITATIONAL SENSING IN
  PLANTS

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• THIGMOTROPISM
• RESPONSE TO TOUCH
• THIGMOMORPHOGENESIS
• THE RESPONSE THAT OCCURS DUE TO MECHANICAL
  CHANGES, WHICH USUALLY CREATES AN INCREASED
  EHTYLENE PRODUCTION
• EX TREES ON A WINDY MOUNTAIN WILL GET THICKER ON
  ONE SIDE IN RESPONSE TO ENVIRONMENTAL STRESSES

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• TRUGOR MOVEMENTS
• RAPID LEAF MOVEMENTS (MIMOSA, VENUS FLY TRAP)
• RAPID LOSS OF TURGOR BY CELLS THAT WILL CREATE
  RAPID LEAF MOVEMENT.
• MAY TAKE UP TO 10 MINUTES TO REGAIN TURGOR

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• SLEEP MOVEMENTS
• POWERED BY DAILY CHANGES IN TURGOR PRESSURE OF
  THE MOTOR CELLS IN PULVINI
• REVERSIBLE CHANGES
• OCCUR IN MANY LEGUMES

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• BIOLOGICAL CLOCKS
• COMMON IN EUKARYOTIC
• CONTROL MANY RHYTHMIC PHENOMENA
• HUMANS BP, BODY TEMP. METABOLISM
• FUNGI SPORES
• PLANTS SLEEP MOVEMENTS

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• CIRCADIAN RHYTHM
• 24 HOUR CYCLE
• MOST CUED INTO LIGHT AND DARK CYCLES, EARTH
  ROTATION
• CLOCK NEEDS TO GET RESET WHEN CLUES CHANGE
• JET LAG, DAYLIGHT SAVINGS

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• PHOTOPERIODISM
• PHSIOLOGICAL RESPONSE TO DAY LENGTH OR HOW PLANTS
  DETECT SEASONAL CHANGES
• SHORT DAY PLANT NEED LESS LIGHT
• LONG DAY PLANT SUMMER PLANTS
• DAY NEUTRAL PLANT UNAFFECTED
• NIGHT LENGTH NOT DAY LENGTH ACTUALLY CONTROL
  FLOWERING

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• FLOWERING HORMONE
• YET TO BE PROVEN
• MERISTEM MUST CHANGE FROM VEGETATIVE GROWTH TO
  FLOWERING GROWTH
• NEEDS A GENE TO BE EXPRESSED IN ORDER FOR THE
  CHANGE TO OCCURE

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• PHYTOCHROMES
• -SPECIAL PIGMENT PHOTORECPETOR MOLECULE WHICH
  MAY CONTAIN A SWITCHING MECHANISM WHICH MIGHT
  EFFECT THE BIOLOGICAL CLOCK

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• PLANTS AND ENVIRONMENTAL STRESS
• ENVIRONMENTAL CONDITIONS THAT CAN EFFECT A PLANTS
  GROWTH REPRODUCTION AND SURVIVAL
• Ex. HALOPHYTE EVOLUTIONARY ADAPTATION IN
  PLANTS TO EXIST IN A SALTY ENVIRONMENT

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• WATER DEFICIT
• PLANTS HAVE CONTROL SYSTEMS IN LEAVES AND ROOTS
  TO HELP COPE WITH WATER STRESS
• REDUCE TRANSPIRATION RATE
• ABSCISIC ACID RELEASE IN MESOPHYL ACT ON GUARD
  CELLS WHICH WILL OPEN TO CLOSE STOMATES
• DECREASE LEAF SURFACE AREA

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• ROOT RESPONSE
• GROW DEEPER TO FIND WATER

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• OXYGEN DEPRIVATION
• OVERWATERED, LOSS OF AIR SPACE TO PROVIDE OXYGEN
  FOR RESPIRATION
• AERIAL ROOTS ADAPTED TO WET ENVIRONMENTS (MARSH
  PLANTS)

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• SALT STRESS
• HALOPHYTES EXCEPTION, SODIUM IS TOXIC TO
  PLANTS,
• OSOMOSIS PLANTS USUALLY WILL LOSE WATER

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• COMPATABLE SOLUTES
• PRODUCED BY PLANT ORGANIC COMPOUNDS THAT KEEP
  WATER POTENTIAL OF CELLS MORE NEGATIVE THAN THE
  SOIL AROUND IT
• SOLUTION WITHOUT ADMITTING TOXIC SALTS
• CANNOT BE DONE FOR VERY LONG

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• HEAT SHOCK PROTEINS
• ABOVE 40 DEGREES CELSIUS
• IDENTICAL TO CHAPERONE PROTEINS, HELP PROTEIN
  FOLD INTO THEIR FUNCTIONAL CONFORMATION, WHICH
  HELPS PREVENT DEHYDRATION
• FOUND IN ANIMALS TOO

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• COLD STRESS
• ALTERS THE FLUIDITY OF MEMBRANE LIPIDS WHICH GET
  LOCKED IN A CRYSTALLINE STRUCTURE
• AFFECTS MEMBRANE TRANSPORT
• REQUIRES SEVERAL HOURS TO OCCUR, SO RAPID
  TEMPERATURE CHANGES ARE STRESSFUL TO PLANTS
• FREEZING SOLUTE COMPOSITION OF THE CYTOSOL
  ALTERS SO IT WILL NOT FREEZE AT 0 DEGREES C.

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• PLANT PROTECTION
• FROM ANIMALS
• PHYSICAL SPINES AND THORNS
• CHEMICAL TOXIC OR DISTASTEFUL COMPOUNDS
• CANAVANINE UNUSUAL AMINO ACID, MADE ONLY BY
  PLANTS SIMILAR TO ARGANINE. WHEN EATEN BY AN
  INSECT IT IS TOXIC AND KILLS THE INSECT
• PARASITOID WASPS INJECT EGGS INTO THEIR PREY
  (CATERPILLAR) LARVAE EAT THEIR CONTAINER AND KILL
  THE HOST

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• PATHOGENS
• VIRUS, BACTERIA AND FUNGI
• PRIME DEFENSE EPIDERMIS
• IF THE PATHOGEN ENTERS THROUGH THE STOMATA OR
  LENTICLE THE SECOND DEFENSE IS CHEMICAL
• GENE TO GENE RECOGNITION, SPECIFIC RESISTANCE TO
  A DISEASE THAT REGULATES A PRECISE MATCH BETWEEN
  AN ALLELE IN THE PLANT AND AN ALLELE IN THE
  PATHOGEN

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• HYPERSENSITIVE RESPONSE (HR)
• A VIGOROUS LOCALIZED RESPONSE TO A VIRULENT
  PATHOGEN
• PHYTOALEXINS ANTIMICROBIAL COMPOUNDS
• P.R. PROTEINS (PATHOGEN RELATED) ANTIMICROBIAL AS
  WELL
• HR RESPONSE INCREASE THE PRODUCTION OF PR
  PROTEINS AND PHTYOALEXINS SO THE INFECTION IS
  SEALED AND WILL CREATE A LOCAL LESION BUT WILL
  NOT DESTROY THE ENTIRE PLANT

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• SAR SYSTEM ACQUIRED RESISTANCE
• CHEMICAL SIGNALS THAT WILL SOUND THE ALARM TO
  PROTECT THE PLANT
• PR PROTEINS AND PHYTOALEXINS WHICH PROTECT THE
  PLANT
• SALICYLIC ACID
• HORMONE RESPONSIBLE FOR ACTIVATING SAR
• CHEW BARK OF A WILLOW TREE (ASPIRIN)