Decrease of total leaf surface, through removal of leaves, affects growth and yield of plants due to less photosynthesis capacity (Moro, Erigoin, 2000). Removal of leaves affects crops yield in different ways. Hailstone, wind, pests and diseases, livestock graze, improper management of herbicides and farming machineries usage are some of the main factors in this regard (Moro, Erigoin, 1998). Leaves were cut to simulate lose of leaves due to natural factors (Haili, Spomer, 1998). Although natural lose of leaves brings in other damages to the plant, determination of these groups of damages is not possible as calculation of the area of lost leaves is not feasible (Bogard, Christian, 2001). In addition to reduction of photosynthesis area, change of canopy structure also reduces the amount of received light (Hatron, 1946), add to that relative growth rate (Krokstone, 1978), water usage performance (Zo, Myeder, 2004), maturation time (Haili, Speech, 1998) and plant hormones (Milford, 1974) and finally product yield.
Irrigation stress during seed development shortens the stage. Intense stress in this stage results in faster physiological growth (18-29%), shorter stage, less production yield (24-44%) and smaller seeds (7-32%) in soybean. Similar results were observed for barely, wheat and maize.