Wind is an important ecological factor that affects plants in several ways. It increases transpiration and heat transfer to leaves, dissipates heat from leaves, causes mechanical damage, scatters pollen, and disperses seeds and fruits. Wind removes the boundary layer of still air around plant surfaces, allowing for gas exchange and cooling leaves. It can also cause desiccation, dwarfing, deformation, lodging, breakage, and abrasion of plants. Many plants are wind pollinated and dispersed, allowing reproduction and spread over large areas. Wind is typically measured using a Robinson Anemometer, which records revolutions of cups on rotating arms to calculate wind speed.

2. TOPIC
WIND AS AN ECOLOGICAL
FACTOR

8. WIND:
Air in motion is called wind .
Wind is an important ecological
factor especially on flat plains
along seacoasts and at high
altitudes in mountains.

9. Winds affects plants directly by:
 Increasing transpiration.
 By delivering heat to relatively cool leaves.
 By dissipating the heat load of isolated
leaves.
 By causing various kinds of mechanical
damages.
 By scattering pollens.
 Dispersal of seeds and fruits.

10. Effects of Wind
on Plants

11. Carbondioxde Replenishment:
Wind removes the bound layer of
still air that covers the surface of a
shoot preventing the diffusion of
oxygen from stomata and co2
towards stomata.

12. Cooling
The boundary layer accumulates heat by
conduction over Epidermis. The wind thins
this layer promoting dissipation of heat
resulting in cooling of the leaf surface. The
cooling effect of wind is detrimental in cold
environment as it limits the physiological
activity of plant.

13. Desiccation
 Air in motion causes evaporation rapidly thus increasing
the rate of transpiration. This results in desiccation
because of removal of water from the tissues, killing
the leaves and twigs, and injuring the fruits. The tall
plants may become low and spreading as a result of
wind action.
 Cushion plants develop in response to desiccation.
These plants consists of stream lined contours
presented by uniform tips of numerous crowded
branches. The action wind on many erect plants mold
their shoot systems into cushion form. When branch
tips are killed, the lateral buds produce vigorous
growth so that each dead terminal is replaced by
several shoots of lateral origin resulting in a cushion
plant.

14. Dwarfing
Turgidity help maturing cells of a plant to
normal sizes. The plants developing under
the influences of drying winds never attain
turgidity that enable them to expand their
maturing cells. As a result all organs are
dwarfed because their cells attain
subnormal size.

15. Deformation
When developing shoots are subjected to
strong wind pressure from a constant
direction, the form and position of the
shoot may become permanently altered.
This called deformation. Trees with inclined
trunks are commonly observed on ridges.
Some trees such as Oaks grow flattened
against the ground while in others the tree
branches develop only in a leeward
direction.

16. Lodging
Lodging is a form of wind injury caused by
violent wind in which the crop plants
(wheat, maize, and sugar cane) flatted
against the ground. But if the stems are not
too mature, the prostrated plants become
partially erect once more by means of
differential growth at the lower node.

17. Breakage
Wind promotes breakage in plants. Trees with
soft and brittle wood are more susceptible to
breakage.
Abrasion
Wind carrying particles of ice or soil is a very
potent abrasive force. Bark and buds may be
eroded away from the windward sides of
woody stem. Crops grown on sandy soils in
wind climates are often damaged in this way.

18. Wind Pollination (Anemophily)
Wind pollination is believed to be primitive form of
pollination. In cool and cold climates that vast
majority of trees, shrubs and herbs are wind
pollinated. Wind pollination has certain
disadvantages. Because of scattering by wind only
few pollen grains are carried to proper kind of
stigmas. Also the wind pollination is very wasteful
since wind pollinated plants have to produce very
large number of pollens. The abundance of pollens
in air causes hayfever in man. However,
anemophily has proved quite successful, since many
plants that dominate the earth’s vegetation are
wind pollinated.

20. Wind Dispersal(Anemochory)
Wind is the most efficient dispersal agent and
most terrestrial plants depend on it to scatter
their disseminules ( seed and fruit ) . The
seeds and fruits have developed certain
adaptations for dispersal such as smaller size
and reduced weight, production of hairs ,
wings etc. so that these may be carried by
wind easily . Similarly seeds and fruit of certain
plants have developed specialized mechanisms
such as tumbling , catapult mechanism, etc for
dispersal by wind.

21. Anemometer-wind Measurement
Wind is usually measure with a Robinson
Anemometer. It consists of a series of three or four
horizontally rotating arms terminated by cups. The
arms are fixed to a vertical shaft which operates a
train of gears motivating a dial. If dial reading are
used, only average velocities can be computer for
the interval b/w readings, but electrical recording
apparatus can be attached which records the time
required for each mile of wind to pass. This
provides a much more useful index of velocities.

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