PLANT GROWTH REGULATORS IN TOMATO CROP PRODUCTION
To study the influences on fruiting, CCC (2.000 ppm), SADH (3.000 ppm) gibberellic acid (GA) 200 ppm, and (2-chloroethyl) phosphonic acid (CEPA) 200 ppm were applied in tomato plants at the fourth true leaf stage of growth. The treatments did not affect the total weight of tomato fruits. These growth regulators did not promote changes in fruit number. Application of CCC and CEPA did not affect the fruit weight average, however, spraying with SADH and GA reduced the fruit weight average (Castro and Malavolta, 1976).
It was studied the relationships between growth regulators, mineral nutrition, osmotic potential, and incidence of blossom-end rot (BER) in tomatoes. The chemicals were applied in tomato plants at the fourth true leaf stage of growth and ammonium sulphate was used to promote the occurence of BER. GA (100 ppm) promoted higher incidence of BER and CCC (2.000 ppm) reduced the occurrence of the physiological disease in relation to control (figure 1A and 1B) (Castro e Malavolta, 1977). Higher levels of N, Ca, and Mg occurred in the stems of plants sprayed with CCC (Malavolta et al., 1975). Treatments with 6-furfurylamino purine (5000 ppm), SADH (4,000 ppm), and CEPA (200 ppm) presented an increase in N level in the stem. CEPA also increased Ca content in stems. These growth regulators did not alter the levels of macronutrients in leaves of tomatoes in relation to control (table 2) (Castro et al., 1979). Plants treated with GA and SADH had a lower (more negative) leaf osmotic potential under water deficit in the soil (table 3) (Castro, 1976).
The auxin 2-hydroxymethyl 4-chlorophenoxyacetic acid was applied at concentrations of 150 and 300 ppm by spraying directed to the clusters in the moment of the opening of the two first flowers in the first cluster. This growth regulator at concentration of 300 ppm increased the average weight of tomato fruits in the four initial harvests. It was noted also a concentration in production of fruits in relation to the control (figure 2) (Castro and Churata-Masca, 1973).