The effects of excess and intimely irrigation on the development of pollen granis an d their grower in soybeans (clark type) were investigated.
Excess irrigation specially in the preflowering and beginning the flowering stages jcauscd significant decrease in the number and growth power of pollen grains. Although the flowers appeared normal but the growth of anthers were abnormal. Many of the anthers before development of the pollen grains were destroyed, and approximately half of the pollen grains in the remained anthers did not show normal feature, size and growth .Most of the destruction happened during segregation of tetraspores and exine formation on the surface of the young microspores. A considerable number of the remained pollen grains lost their growth power and formation of the pollen grain tube.
It is concluded that a considerable decrease in the number of normal pollen grains and their growth power is due to excess and untim ely irrigation and it can be a factor in declining the frop.