Paclobutrazol is a trizole fungicide known to have growth retardant properties. This study was conducted to estimate the influences of paclobutrazol (100 mg L-1) on the photosynthetic capacity, as well as the morphological and anatomical features of wheat cv. Sakha 93 sown at different dates, the normal sowing date (november, 26), early sowing date (October,16 ), as well as late one (January, 4). Fluorescence changes appeared to be high-sensitive to chlorophyll decrease before any other visual signs has been observed; the degree of stress was quantified through changes in leaf pigments. The deteriorative symptoms of the early and late sowing indicated by reduction in chlorophyll (a & b) and the increase in fluorescence ratio F680/F730 were ameliorated by paclobutrazol pre-treatment. PBZ pretreatment increased shoot length, stem diameter, leaf area, fresh and dry weights and spike yield of wheat plants at the different sowing dates. The increments of epidermal cell length and width, number of trichomes and crystals (druses), as well as the number of xylem vessels were measured in PBZ-pretreated wheat leaves and stems. Likewise, a concomitant decrease in vessels width and thickness, intercellular spaces and stem pith. The results presumed that PBZ probably contribute to some extent to nullify the damage of the flocculated temperature displayed during different sowing dates thereby enhanced wheat growth and productivity.
Key words: Wheat, Paclobutrazol, Early sowing, Late sowing, Leaf, Stem, Anatomy, Chlorophyll, Fluorescence
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