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