Effect of the Retardant "Dextril" on the Quality of Tomato Seedlings Grown at High Temperature Conditions

The effect of different concentrations of growth retardant "Dextril" (C11 H18Cl2O7P) on tomato (Solanum lycopersicum c.v Huda F1) seedlings quality was studied, at the Agriculture Faculty of Alexandria - Egypt, on 2010. Tomato seedlings were sprayed when the second true leaf was appeared with "Dextril" at (0.02 – 0.04 – 0.06 – 0.08 – 0.1%) levels, to promote seedlings tolerance to heat stress during summer – autumn period and limit stem growth and elongation. The results showed that, "Dextril" treatment of (0.02 -0.04 – and 0.06%) levels improved seedlings quality and decreased stem height by 30, 32 and 35% respectively compared to the control, whereas, 0.08 and 0.1% levels showed toxic effects. Treatment with "Dextril" increased as well, stem diameter, fresh and dry weight of shoots but it did not affect leaf number compared to the control. The results indicate that the spraying with low concentrations of ‘Dextril” is promising measure for improving the stress response and developmental characteristics of tomato seedlings grown under high temperature conditions.