DRY-MATTER PRODUCTION AND UPTAKE OF ZINC AND PHOSPHORUS IN 2 OILSEED RAPE GENOTYPES UNDER DIFFERENTIAL RATES OF ZINC AND PHOSPHORUS SUPPLY

The effects of varied supply of zinc (Zn) (0, 0.1, 0.2, 1.0, and 10 mg Zn kg(-1) soil) and phosphorus (P) (low P: 50 mg P kg(-1) soil and hi gh P: 150 mg P kg(-1) soil) on vegetative growth, plant tissue Zn and P concentration and their uptake were studied in six weeks old plants of two oilseed rape (Brassica napus) genotypes (92-13, a traditional g enotype from China high in both erucic acid and glucosinolate, and Xin za-2, a hybrid from China low in erucic acid and glucosinolate) grown in Laffer sand (low in Zn and P) under controlled environmental condit ions. Two oilseed rape genotypes had a differential response to Zn app lication. Xinxa 2 responded significantly for shoot and root dry matte r only up to 0.1 mg applied Zn kg(-1) soil, while 92-13 responded up t o 0.2 mg Zn kg(-1) soil. Zinc at 10 mg kg(-1) soil slightly reduced sh oot dry matter and drastically reduced root dry matter of both the gen otypes. Shoot and root dry matter production at 0, 0.1, 0.2, and 1 mg Zn kg(-1) soil were significantly greater under high P supply compared with low P supply. High P supply did not accentuate Zn deficiency sym ptoms compared with low P supply even at nil Zn. Phosphorus concentrat ion in plant parts was significantly higher at nil Zn compared with Zn application. An increase in P supply had a non-significant effect on Zn concentration, but significantly increased the P concentration and P uptake in shoots. The results suggest that an increased supply of P at lower rates of Zn application was not detrimental for early vegetat ive growth and 2n uptake of two oilseed rape genotypes.