Page 41 - Introduction to Agriculture by: Aqleem Abbas

Introduction to Agriculture Notes prepared by: Aqleem Abbas

Environmental factors are divided into five groups;
1. Climatic factors
2. Water factors i.e. hydrophytes, xerophytes and mesophytes
3. Topographic factors or slope or elevation
4. Edapic factors i.e. soil factors, soil structure, soil texture.
5. Biotic factors ; biotic factors are also important for growth and life of plants

Classification of crops on the basis of pollination

Pollination

The transfer of pollen grains from anther to stigma of a flower. Based on pollination we have divide crops
into two types

Self pollinated crops or autogamy

These crops in which pollens are transferred into the stigma of same flower, different flower on same
plant and different flower on different plants of same cultivar. Self fertilized plants have close flower but
1 to 3 percent cross pollination can be occurred.

For example wheat, barley, rice and soybean

Cross pollinated crops (allogamy)

Transfer of pollen grains to stigma of different cultivars. It is carried out by insect, wind and water. They
have open type flower. Cross pollination occur to an extent of 96 percent e.g. maize, safflower, sunflower,
and brassica. Cross pollination by wind is called anemophily while by insect it is called entomophily.

Some reasons for allogamy

1. Self incompatibility
2. Dichogamy a. protandry (pearl millet) anther ripe before carpel. B. protogamy.
3. Cytogenetic reasons. A. translocation, aneuploidy, autopolyploidy.
4. Hetrostyle
The situation in which the stamen and style of unequal length for example
Pinflower have long pistil and short anthers.
Thrumb flower have long stamens and short pistil.
Floral mechanism
Cleistogamy
Their flower donot open and are internally pollinated and fertilized. It is
autogamy.
Chasmogamy
When pollination occurs after opening of flower. It may be autogamy or
allogamy.