Temperature in relation to phosphorus nutrition in Chinese cabbage

Chinese cabbage plants [Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50] we re cultivated experimentally for two years (1993 and 1994) using a semi-for cing technique of floating rowcovers, polyethylene (T-1), polypropylene (T- 2), versus no floating row-covers, control (T-0). 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 we ll as foliar acid phosphatase activity (FAPA). The aerial and root temperat ures of the treatments T-1 and T-2 exceeded those of T-0. The P-total conce ntration showed no significant variations with treatment, whereas the P-i c oncentrations increased in T-1 and T-2 and P-org decreased in both treatmen ts with respect to T-0. The FAPA was influenced a similar way as Pi, raisin g with temperature. The contents (mg plant(1)) of P-total, P-i, and P-org w ere greater in T-1 and T-2 than in T-0, and this could be due to the fact t hat the highest temperatures (root and aerial zone) generated by the plasti c rowcovers favored the absorption of P, thereby boosting FAPA and the fres h and dry weights, and yield.