Temperature in relation to phosphorus nutrition in Chinese cabbage

Abstract

Chinese cabbage plants [Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50] were cultivated experimentally for two years (1993 and 1994) using a semi‐forcing technique of floating rowcovers, polyethylene (T₁), polypropylene (T₂), versus no floating row‐covers, control (T₀). Five samplings were made, taking four plants per each replication and total phosphorus (P) (P_total), inorganic P (P_i), and calculated organic P (P_org) were determined as well as foliar acid phosphatase activity (FAPA). The aerial and root temperatures of the treatments T₁ and T₂ exceeded those of T₀. The P_total concentration showed no significant variations with treatment, whereas the P_i concentrations increased in T_i and T₂ and P_org decreased in both treatments with respect to T₀. The FAPA was influenced a similar way as P_i, raising with temperature. The contents (mg plant^‐1) of P_tolal, P_i, and P_org were greater in T₁ and T₂ than in T₀, and this could be due to the fact that the highest temperatures (root and aerial zone) generated by the plastic rowcovers favored the absorption of P, thereby boosting FAPA and the fresh and dry weights, and yield.