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The AMBIENT ENVIRONMENT

The AMBIENT ENVIRONMENT. Light and Temperature. LIGHT and PHYTOCHROME. Pigment PHYTOCHROME Blue-green pigment Exists in two forms Pr (660 nm) Pfr (730 nm) Amount of Pr or Pfr in tissues is determined with the type of light present. PHYTOCHROME.

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The AMBIENT ENVIRONMENT

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  1. The AMBIENT ENVIRONMENT Light and Temperature

  2. LIGHT and PHYTOCHROME • Pigment PHYTOCHROME • Blue-green pigment • Exists in two forms Pr (660 nm) Pfr (730 nm) • Amount of Pr or Pfr in tissues is determined with the type of light present

  3. PHYTOCHROME • Pr is SYNTHESIZED by the plant and very STABLE • Pfr is NOT STABLE • Slowly reverts back to Pr in the DARK or in SHADE • Highest CONCENTRATIONS found in the MERISTEMATIC TISSUES • Apical meristems • Cambium meristems

  4. PHOTOMORPHOGENESIS • Plant SENSES the RATIO of Pr to Pfr which influences HORMONES and stimulates a RESPONSE • PHOTOMORPHOGENESIS - Growth and development in response to light • SEED GERMINATION • BRANCHING and STEM ELONGATION – ETIOLATION • LEAF MOVEMENTS • ANTHOCYANIN PRODUCTION • FLOWERING and PHOTOPERIODISM

  5. PHOTOMORPHOGENESIS • BRANCHING and STEM ELONGATION • ETIOLATION • Leaves absorb RED & FAR RED light selectively • 90% of RED LIGHT absorbed by leaf • ~ 2% of FAR RED light absorbed • Higher % of Pr activates GROWTH HORMONES (Gibberelins) allows plant to REACH for light

  6. PHOTOMORPHOGENESIS • LEAF MOVEMENTS • CLOSURE of LEAFLETS at night • Higher % of Pfr increases closure • Cells at attachment points to midrib (pulvini) gain turgor pressure due to water and potassium ions and leaflets open • Loss of turgor leaflets close • PHYTOCHROME thought to affect permeability of the cellular membrane and ion movement across it.

  7. PHOTOMORPHOGENESIS • ANTHOCYANIN PRODUCTION • During SUNNY DAYS and COLD NIGHTS in fall • Pigments form from high concentrations of SUGARS in CELL • FAR RED light stimulates Anthocyanin production • SHORTENING DAYLIGHT increases more time in FAR RED light (or DARKNESS) which increases more Pr in plant (Pr 97% - Pfr 3%)

  8. PHOTOMORPHOGENESIS • FLOWERING and PHOTOPERIODISM • PHOTOPERIODISM is the RESPONSE of plants to CHANGING LENGTH of DAYS and NIGHT • DAYLENGTH is important, but plants happen to be more responsive to PERIODS of DARKNESS • % of Pfr which depletes during darkness is primary factor

  9. PHOTOMORPHOGENESIS • PHOTOPERIODISM is CUMULATIVE • Called CRITICAL DAYLENGTH (CDL) and is species dependent • SHORT DAY – daylength < CDL • LONG DAY - daylength > CDL • DAY NEUTRAL – NOT DAYLENGTH dependent • Also SD or LD plants can be grouped by: • OBLIGATE – must have DAYLENGTH requirement to flower • QUANTITATIVE – plant will FLOWER FASTER or MORE if exposed to proper DAYLENGTH

  10. PHOTOMORPHOGENESIS • PHOTOPERIODISM

  11. PHOTOMORPHOGENESIS • PHOTOPERIODISM related to many PROCESSES • Mostly related to FLOWER INITIATION, but also related to: • FORMATION of STORAGE ORGANS • STEM ELONGATION • FALL COLOR, LEAF AGING, & ABSCISSION • BUD DORMANCY

  12. TEMPERATURE • Plants EVOLVED with the earth’s various TEMPERATURE regimes • Limited to 0° – 50° C (32° – 122° F) • @ 0° C (32° F) biological ACTIVITY SLOWS or STOPS • @ > 50° C (122° F) PROTEINS destroyed, PLANT INJURY or DEATH • BEST GROWTH @ 10° - 30° C (50° – 85° F) • As TEMPERATURE RISES every 10° GROWTH can increase 1.3 – 5 X’s (2 X’s average) • Growers use this fact to INCREASE or DECREASE GROWTH

  13. TEMPERATURE • THERMOPERIODICITY • Is the FLUCTUATION of DAY and NIGHT TEMPERATURES • Most plant GROWTH occurs at NIGHT • Plants from GROW BETTER with THERMOPERIODICITY • Important to TEMPERATE CLIMATE plants • Not so important to tropical plants

  14. TEMPERATURE • VERNALIZATION • The INITIATION of FLOWERING in plants by exposure to EXTENDED COLD PERIODS • CHILLING REQUIREMENTS • ABSOLUTE – specific number of DAYS BELOW a certain TEMPERATURE • QUANTITATIVE – flower EARLIER and MORE with exposure to COLD • Stimulus is perceived in the APICAL MERISTEM • HIGH TEMPS can REVERSE or DEVERNALIZE plants

  15. TEMPERATURE • DORMANCY • DORMANCY is state of INACTIVE GROWTH due to INTERNAL and EXTERNAL FACTORS • KEY to SURVIVAL of PERENNIAL plants growing in TEMPERATE or COLD CLIMATES • Plants BREAK DORMANCY when ENVIRONMENTAL CONDITIONS are FAVORABLE for GROWTH and DEVELOPMENT

  16. TEMPERATURE • DORMANCY is a gradual process that STARTS as GROWTH TAPERS in SUMMER • TRIGGERED by: • SHORTENING DAYS • LOWER TEMPS • DROUGHT • STEPS to PLANT DORMANCY: • PHOTOSYNTHESIS SLOWS or STOPS • GROWTH STOPS • TRANSLOCATION of FLUIDS reduced • Decreased ENERGY REQUIREMENTS • PROGRESSION through plant • AXILLARY buds >> TERMINAL buds >> BRANCHES >> TRUNK >> BARK last • ROOTS never become truly dormant, they CONTINUE to GROW as long as SOIL TEMPS > 40 degrees

  17. TEMPERATURE • HARDINESS and ACCLIMATION • HARDINESS - The ability of a DORMANT plant to withstand COLD TEMPS without severe TISSUE DAMAGE • ACCLIMATION - the ability to DEVELOP HARDINESS • DEGREE of HARDINESS changes in RESPONSE to the ENVIRONMENT, and the responsiveness of the plant DEPENDS on it’s GROWTH STAGE (see handout)

  18. TEMPERATURE • DEGREE of COLD HARDINESS DEPENDS on: • GENETICS of the plant and the HABITAT and CLIMATE it originally ADAPTED to • GROWTH STAGE • FOOD STORED in the plant • LOW RESERVES in the plant will LOWER COLD HARDINESS • Poor nutrition • Heavy foliage, flower, fruit production • Shortened growing period • Excessive forced growth from high N fertilization

  19. TEMPERATURE • PHYSIOLOGY of ACCLIMATION • The FORMATION of ICE CRYSTALS damages cells • Plant have a variety of WAYS to KEEP SAP from FREEZING • CONVERSION of STARCH to SUGARS in CELLS • Increased VISCOSITY or THICKNESS of CELL CYTOPLASM • ICE CRYSTALS form in the INTERCELLULAR SPACES • DEHYDRATES CELL - draws more water out of cell due to osmosis • Makes content of cell MORE VISCOUS • “SUPERCOOLING” sap • Some plants have the ability to “SUPERCOOL” fluids below the freezing point without freezing their tissues

  20. WINTER INJURIES • WINTER DESICCATION • DRYING out of TISSUES • PREVENTION: • WATER when ground thawed • MULCHING to retain moisture • WINDBREAKS to decrease transpiration • ANTI – DESICCANTS sprays reduce transpiration for a few days, good for transplanting

  21. WINTER INJURIES • FREEZE INJURY • SUDDEN DROP in TEMP or EXTREME TEMP CHANGE • PREVENTION: • MULCH WHOLE plant • SPRAYING ORCHARDS with WATER • As water freezes HEAT is released, continually freezing water protects tissues • @ 32 degrees F

  22. WINTER INJURIES • FROST HEAVING (roots) • PREVENTION: • MULCHING • Better DRAINAGE • ONCE HAPPENS - PRESS plants DOWN into ground • FREEZING of CONTAINER PLANTS (roots) • PREVENTION: • GROUP together • HEAL into MULCH

  23. WINTER INJURIES • ICE DAMAGE • SNOW DAMAGE • PREVENTION: • STAKE or PROP small trees and shrubs • Proper PRUNING and THINNING • SLOW GROWING TREES

  24. WINTER INJURIES • BARK SPLITTING or FROST CRACKING • SUDDEN FREEZE before the tree attains HARDINESS causes the BARK to SPLIT along the CAMBIUM LAYER • PREVENTION: • Protect by WRAPPING with burlap, tree guards, white paint • Plant more RESISTANT, THICKER BARK SPECIES • ONCE HAPPENS – WRAP TRUNK or TACK BARK BACK to protect as much cambium and phloem tissue from drying out

  25. WINTER INJURIES • WINTER SUNSCALD or SW INJURY • Sunny winter day, with a cold nights • Causes bark to deacclimatize and become susceptible to freezing • PREVENTION: • Protect by WRAPPING with burlap, tree guards, white paint • Plant more RESISTANT, THICKER BARK SPECIES

  26. SUMMER INJURIES • WATER and HEAT STRESS • SUMMER SUNSCALD

  27. SUMMER INJURIES • WATER and HEAT STRESS • SUMMER SUNSCALD • PREVENTION • Adequate WATER in soil • MISTING plants

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