Q. How is wind helpful for plants?
Wind is an important ecological factor which affects both directly and indirectly. The direct effects of wind are to be seen in the regions which are quite often exposed to violent winds. Violent winds often break off twigs or branches of plants and sometimes even uproot the trees and shrubs. Such an effect of wind often prevents the growing of larger trees above a certain height. The vegetation of such areas is mostly composed of species which have a prostrate habit of growth and a tenacious underground root or rhizome system.
Larger plants which are often exposed to violent winds and are adapted to such condition have following important characters:
(i) Their trunk and branches are often bent,
(ii) The branching is irregular,
(iii) The crown presents a very peculiar shape, and
(iv) The leaves are smaller than usual. Sometimes fast, cold winds result in cushioned growth in plants—e.g., Androsace helvetica,
(v) some plants that grow in areas subjected to strong wind all the year round develop an overall shape that offers least resistance to wind.
Thus growth is restricted on the side on which wind effect is most. Its effect is quite common on sea cost and mountain plants as there the wind is more effective in killing buds and thereby checking branch development on windward side (Fig. 1.2).
Indirect effects of wind are more significant. Wind velocity has great effect on the rate of transpiration of plants. As the fast blowing air currents remove layers of humid air from the vicinity of leaf surface, rate of transpiration markedly increases. With the increasing altitude, wind velocity also increases thus promoting the rate of transpiration. Plants growing at higher altitudes show stunted growth because of the effects of wind.
The plants growing at lower altitudes have less chances of being put to the effects of violent winds and undergoing excessive transpiration due to wind action. On account of the wind action, the height at which a plant can grow depends on its ability to absorb and transport water rapidly enough to replace that lost as a result of transpiration. A plant cannot survive under conditions where loss of water by transpiration is greater than gain in water by absorption from the soil.
Wind action will be most severe when soil temperature is extremely low. Very low temperature of soil almost or entirely arrests the absorption of water by the roots. While a majority of plants are very sensitive to wind actions, some show great degree of adaptability. For instance, Vaccinium myrtillus is a comparatively large bush two to three feet high under normal conditions, while growing on high mountains develops underground rhizome and root system and its aerial branches do not project more than an inch above the soil surface.
Courtesy of the NYBG Plant Information Service