Response of Rockwool-grown Greenhouse Cucumber, Tomato, and Pepper to Kinetin Foliar Sprays

Abstract

Encouraging results from previous trials on field vegetables led to the expectation that a kinetin foliar spray from the commercial product KIN-Gro (5000 ppm kinetin) on greenhouse vegetables would positively affect their growth and productivity. Thus, in this study, we evaluated the usefulness of this product on rockwool-grown `Bodega' cucumber (Cucumis sativus), `Rapsodie' tomato (Lycopersicum esculentum), and `4-Ever' and `444' pepper (Capsicum annuum) at the Greenhouse and Processing Crops Research Centre of Agriculture and Agri-Food Canada, Harrow, Ont. Two replicated experiments were conducted to study the effect of kinetin spray on growth and production of all three crops: the first in Spring-Summer 2004 and the second in Fall-Winter 2004. Foliar sprays of kinetin at 2.5, 5, and 10 ppm concentrations were tested against a water spray (control) on each crop. A 2.5-ppm kinetin spray had beneficial effects on the growth of cucumber transplants (taller plants and greater leaf area and fresh weight of leaves and stems). Furthermore, this treatment resulted in higher marketable yield in the Spring-Summer crop and in larger fruit size in the Fall-Winter crop. Regression analysis showed that cucumber marketable yield had an overall quadratic response to kinetin spray concentration in Spring-Summer season maximizing at 5.1 ppm kinetin. Kinetin spray also had beneficial effects on the growth of tomato seedlings, but not on yield. On the other hand, significant beneficial effects were observed on the growth of pepper seedlings and on marketable yield and fruit quality. Regression analysis showed that the response of pepper marketable yield to kinetin spray concentration was positive and linear. It must be noted that, given the rather short-term nature of our experiments, the observed beneficial effects of the kinetin sprays on yield can only be interpreted as beneficial effects on early yield rather than on the total yield. We concluded that under our growing conditions, cucumber production would benefit from a dilute (2.5 ppm) kinetin spray, and pepper production from a high concentration spray (10 ppm); tomato transplant growth will also benefit from a kinetin spray at 2.5 ppm. The results of this study could be of considerable significance to the greenhouse vegetable industry.