The effect of plant-growth regulators on the production of out-of-season greenhouse tomatoes (Lycopersicum esculentum)

Abstract

The yield of greenhouse tomatoes produced in spring and midwinter is reduced by unfavourable environmental conditions involving low temperatures and low light intensities. This study has evaluated the role of various plant growth regulators including: synthetic cytokinin (CPPU) at 1ml.L−1, auxins 1-naphthylacetic acid at 1ml.L−1 and 4-chlorophenoxyacetic acid (4-CPA) at 30mg.L−1, gibberellins (GA3) ‘ProGibb 4%′ and SupaGibb 4SL’ both at 1ml.L−1, and a mixture of benzyladenine (6-BA) plus GA4+7 at 1ml.L−1. Treatments were applied in improving fruiting characteristics of out of season tomatoes up to three times successively when three or more flowers of an inflorescence reached anthesis. PGR's, CPPU, 1-NAA, 4-CPA, ‘ProGibb’, ‘SupaGibb’ and BA plus GA4+7, at three applications, induced higher tomato yields by increasing the truss mass. Synthetic auxins, 1-NAA and 4-CPA, increased the average fruit mass as well as the number of fruit with a diameter larger than 37 mm but also increased the percentage of malformed fruit. Three applications of the mixture BA plus GA4+7 provided the most promising results by improving the yield of marketable fruit through increases in the number of fruit set, the number of fruit per truss and the overall truss mass. No detrimental affects on fruit shape were associated with this treatment.