Growth Responses of Tomato Plants in Non-aerated Water Culture to Foliar Sprays of Gibberellic Acid and Benzyladenine

Tomato plants were grown to the five-six leaf stage in aerated water culture and aeration then discontinued. Foliar sprays of gibberellic acid (G), N6 benzyladenine (B), and ammonium nitrate (N) were applied for periods up to 7 days and the plants harvested on the eighth day. A mixture of 2·5 ppm G, 5·0 ppm B, and 280 ppm N increased growth of the whole plant and this was attributable almost entirely to G and B. In the leaf, both increased water content (B>G) and dry weight. G, but not B, increased leaf area; B, but not G, increased fresh weight leaf/unit area. In the stem, G increased dry weight and height; B reduced height but increased diameter and water content. Inclusion of O·I ppm indol-3yl-acetic acid in the mixture was ineffective. The percentage increase in growth of non-aerated plants with G+B+N was greater with non-acrated than with aerated plants for weight of whole plant and leaf area, but not for stem height. Growth of non-aerated plants could not be increased by increasing the volume of the nutrient solution, by ‘aerating’ with nitrogen, or by applying minerals in foliar sprays.