Irrigation discontinues at 50 % of flowering time showed maximum panicle height (24.50 cm), number of panicle
per M2 (486.22) and grain yield (408.78 g/M2). Maximum (22.75 g) and minimum (21.11 g) 1000-seed were
obtained in treatment of irrigation discontinue at the beginning and middle of tillering respectively. Silicon amounts
had no significant effect on yield components (Table 2). Maximum leaf area is necessary for yield increasing, so
irrigation discontinue at this time is reason to reduce in dry weight of shoots and then decrease in number of stem
per unit/panicle, therefore diminish flexibility in cell wall and osmotic potential. Deficiencies of water affect on cell
expansion by change of physical and metabolic, to limited leaf area, to prevent light absorption and decrease in
photosynthesis and grain yield [10]. Silicon increase growth by increase in number of tiller, leaf area, activity of
photosynthesis in lower leaves and also cause to be vertical position and stability in rice leaves and to increase
percentage of filled spikelets and grain yield [5].