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Wind : Effects
WIND
DIRECT EFFECTS
AIR FLOWMECHANICAL
(THIGMOTROPISM)
INDIRECT EFFECTS
SOIL EROSION & ABRASION
DISEASE SPREAD
INDIRECT EFFECT
DIRECT EFFECT
DIRECT EFFECT
DIRECT EFFECTS
• Wind: affect development and alter morphology
• Wind exposed plants: fewer, smaller leaves which contain a higher proportion of mechanical tissues
• Wind : Complex phenomenon
DIRECT EFFECTS
• Stress due to wind flow and mechanical stress : both have different effects– responses of plants to wind :
• depend on the relative importance of air flow and mechanical stress effects
• depend on the overall environmental conditions as well as the characteristics of the plants themselves.
– factors include• humidity• the magnitude, frequency and duration of wind loading• leaf shape and size and the overall shape • drag coefficient of the vegetation stand in which a plant is
growing
• Induce stress in
– Leaves
– Stem
– Roots
– Other parts
• The decrease yield due to wind exposure
– 30% for sorghum
– 24% for barley
– 48% in the marigold
DIRECT EFFECTS
Wind stress in leaves
• leaves are probably most strongly influenced
• A gentle breeze - increase the photosynthesis -low winds reduce the thickness of LEAF boundary layer – decrease resistance to movement of carbondioxide into the leaf
Wind stress in leaves
• strong winds – reduce photosynthesis
• lowering leaf temperatures below the optimum, reducing stomatal conductance to prevent excessive water loss
• by causing leaves to roll up or curl inwards, which reduces their effective leaf area (Telewski, 1995).
• The precise effect :depends on the morphology of the leaves, the optimal temperature of the photosynthetic enzymes, and the wind speed as well as other environmental factors
Wind stress in leaves
• Higher transpiration reduces leaf temperature and may dehydrate plants
• Leaves with large surface area to volume ratios -maximizes the light capture per mass invested – prone to mechanical failure under bending and
tearing by wind forces (Wilson, 1984)
Wind stress in leaves• Reduced biomass in leaf lamina and petioles -
reduced leaf size and flexural stiffness of petioles-reduced mechanical loads and increased leaf flexibility (Read & Stokes, 2006).
• Leaves of wind-exposed plants had thicker laminas and tended to have higher water content
• Wind-exposed plants also had shorter petioles and rounder (relatively shorter and wider) leaf blades
• wind-induced phenotypic changes in at least some leaf traits were associated with preventing dehydration
Stress in stem
• Inhibition of stem elongation, and increases in stem diameter and root allocation (Jaffe & Forbes, 1993; Telewski & Pruyn, 1998)
• These responses, denoted as thigmomorphogenesis - increase a plant’s resistance to mechanical stress
Stress in stem• Can induce responses that are different those
induced by pure mechanical stress: production of thinner more elongated stems under wind loading (Henry & Thomas, 2002; Smith&Ennos, 2003).
• A reduction in flexural stiffness-increases flexibility-ability to reconfigure under wind loading
• STEM TENDRILS
Stress in stem• Trees : increases in the amount of secondary wood - producing thicker
trunks and roots
• "flexure wood" to describe the extra wood formation found in tree stems as a result of bending
• “reaction wood” - forms when the stem is permanently displaced
• Flexure wood is more dense than normal wood- with a smaller tracheidlumen size and microfibrils in the cell wall
• Flexure wood is more rigid with a greater inertia and flexural stiffness than normal wood-maintain the stem in a vertical position during windy conditions
Effect on roots
• changes in root development-enhance anchorage strength
• Root architecture and uprooting strength
• Secondary thickening of stem is continuous with that in the top lateral roots
• Increase in stem radial growth may be reflected in root growth.
• influence the resistance to bending of the roots and hence improve anchorage strength.
Effect on roots
• increase in the numbers of large roots• more branched than the roots growing
perpendicular to the wind direction• The higher the concentration of roots per unit
area of soil, the greater the tensile strength• when branching becomes more random on the
windward side only, resistance to overturning increases.
Signals and wind responses
• Hormones
• secondary messengers
• nitric oxide (NO)
• reactive oxygen species (ROS)
• lipid-derived metabolites
Potential signaling factors.
Calcium
• Calcium (Ca2+) is a universal signal transduction molecule
• Plants can’t tolerate Ca2+ levels outside the cells (10-3 M)
• Cytosolic Ca2+ at low concentrations by active removal to extracellular spaces or to intracellular organelles
Wind/ Perturbation
CytosolicCa2+
increases
TCH genes activated
Ca2+ sensors :Calmodulin (CaM) &
Calmodulin like proteins (CAL)
Activation
Modulate target enzymes
Physiological response
JASMONATES
• Jasmonates (JAs) are a family of cyclopentanone derivatives synthesized from linolenic acid via the octadecanoid pathway.
• Lipid-derived metabolites, which include jasmonic acid (JA), its methyl ester (MeJA), and 12-oxo-10,15-phytodienoic acid (12-OPDA)
JASMONATES
• Implicated in plant thigmomorphogeneticresponses to mechano-stimulations
• Intracellular MeJA levels in coiling tendrils are more elevated compared with those from already coiled ones
perturbation
Increase Ca2+ levels
Localisation of PLD to membranes
Active PLD
Free polyunsaturated FA
jasmonates
Thigmomorphogenic response
Increase (LOX) transcripts
PLD= phospholipase DLOX= lipoxygenase
ETHYLENE
ACS = 1-aminocyclopropane-1-carboxylate synthase
Stimuli
Up regulation of ACS
Enhanced Ethylene production
Interact with other growth hormones
Thigmomorphogenicresponses
ABA
• Abscisic acid (ABA) –regulates stress responses and developmental processes
• The in vivo accumulation of ABA retards and/or suppresses plant growth
• GROWTH RETARDATION
• MECHANISM NOT CLEARLY KNOWN
AUXIN
• Mechanical stimulation of soybean and pea plants reverses auxin-promoted shoot elongation
• A major mechanism for auxin turnover is peroxidase-mediated oxidative decarboxylation
• An increase in the peroxidase activity occurs in mechanically perturbed plants
(PID) = pinoid =serine/threonine protein kinase
Stimuli
Ca 2+ sensor TCH3
Regulation of PID
Regulate auxinregulators (PIN family)
Auxin signalling and thigmomorphogenesis
Nitric oxide
• Nitric oxide (NO) is involved in regulating various developmental and physiological processes in plants, including seed germination, cell differentiation, transition to flowering, and Senescence
• the function of CML24 is required for appropriate NO production and accumulation
• CML24 in transducing Ca2+ signals important for regulating NO accumulation.
Reactive oxygen species
• Plants subjected to various environmental stresses, including mechanical stress, accumulate hydrogen peroxide (H2O2) and superoxide O2 , reactive oxygen species (ROS)
• Cells may utilize ROS as signalling molecules to regulate the expression of genes
•Reduction of plant height :large increases in yield :due to lodging resistance, improved harvest index, and more efficient utilization of the environment•involvement of the dwarfing genes with the gibberellinbiosynthesis, •Dwarf mutants : GA biosynthetic and signal transduction pathway•1917, the dwarf wheat genotype ’Daruma’ was crossed to ‘Fultz,’ a landrace imported from the United States to Japan•1925, Japanese breeders crossed ‘Daruma’—‘Fultz’ with ‘Turkey,’ a Russian wheat land race•Selection of ‘Norin10- released in Japan in 1935- stiff, short stemmed wheat varieties
• S. C. Salmon introduced 16 varieties of this plant type to the United States: available to breeders in 1947–1948.
• The crosses between ‘Norin10’ and the American varieties : first variety ‘Gaines’ was released in 1962 (Morrison and Voguel, 1962)
• Voguel sent lines of this cross in 1953 to Norman Borlaug- CIMMYT in Mexico
• Borlaug used them intensively to develop new types of wheat :responsible for the “Green Revolution
• Dwarf mutants defective for different steps in the GA pathway
GA sensitiveCrop Dwarfing genes
maize, an, d1, d2, d3, and d5
wheat, Rht4, Rht6, Rht7, Rht8,Rht9, Rht11, and Rht17 are recessive genes; Rht12 is a strong dominant gene
the rye Ddw1, Ddw2 (dominant genes), and d2 (recessivegene)
oat Dw6, Dw7, and Dw8
GA insensitiveCrop Dwarfing genes
wheat Rht1 and Rht2 genes(norin 10)
rice sd1 from ‘Dee-geo-woo-gen’
maize d8 and d9 genes in
Wheat Rht-B1b, Rht-D1b, Rht-B1c, and Rht-D1c