INFLUENCE OF NITROGEN, PHOSPHORUS, AND POTASSIUM ON PIGMENT CONCENTRATION IN CUCUMBER LEAVES

Cucumber plants (Cucumis sativus cv. Brunex) were grown under controll ed conditions and submitted to an individual fertilization with differ ent doses of N (N1 = 5 g/m(2); N2 = 10 g/m(2); N3 = 20 g/m(2); N4 = 40 g/m(2)) as NH4NO3, P (P1 = 7 g/m(2); P2 = 14 g/m(2)) as H3PO4, and K (K1 = 20 g/m(2); K2 = 40 g/m(2)) as K2SO4. This fertilization was appl ied together with organic matter and a micronutrients solution, with d oses standard throughtout the plant's biological cycle. Control plants were included in the experimental design. Cucumber leaves were collec ted every 15 days during the plant life cycle, bing assayed for their chlorophyll a and b (Chi a and Chl b), carotene, and licopene contents . Our results showed that N fertilization induced an increase of 15% i n Chll a respect to the control plants for the N3 treatment, whereas t he N4 treatment resulted in a decrease in Chi a. Chlorophyll b present ed a similar behaviour as that for Chll a, with a 10% increase occurri ng with the N3 treatment. Carotenes behaved in a same manner as that f or chlorophyll, while the licopenes did not show any significant varia tion among treatments. Inversely, P fertilization induced a decrease o f both chlorophyll a and b with the P2 treatment, whereas P did not af fect accessory pigments concentration. The K2 treatment acted positive ly on the chll a and carotene levels with an 1.1% and 7% increase as c ompared with the control plants, respectively. Chlorophyll b did not v ary significantly due to the K doses. In summary, our results showed t hat N affected the pigment content, specially the photosynthetic pigme nts, while high doses of P acted negatively on all the pigments studie d.