SEED ZINC CONTENT INFLUENCES EARLY VEGETATIVE GROWTH AND ZINC UPTAKE IN OILSEED RAPE (BRASSICA-NAPUS AND BRASSICA-JUNCEA) GENOTYPES ON ZINC-DEFICIENT SOIL

Low-Zn seed (around 80 ng Zn per seed) and high-Zn seed (around 160 ng Zn per seed) of Zhongyou 821 (a traditional Brassica napus genotype f rom China found to be Zn-inefficient in our previous experiments), Nar endra (Zn-efficient B. napus genotype from Australia) and CSIRO-1 (a Z n-efficient B. juncea genotype from Australia) oilseed rape genotypes were sown in pots containing Zn-deficient siliceous sand fertilized wi th low Zn supply (0.05 mg Zn kg(-1) soil) or high Zn supply (2.0 mg Zn kg(-1) soil) in a controlled environment. After six weeks, plants der ived from the high-Zn seed had better seedling vigour, increased root and shoot growth, more leaf area and chlorophyll concentration in fres h leaf and higher Zn uptake in shoot compared to those from low-Zn see d at low Zn supply; the impact of high-Zn seed was more marked in Zhon gyou 821 compared with CSIRO-1 and Narendra. The influence of high-Zn seed was dissipated at high Zn supply. CSIRO-1 was superior in terms o f shoot dry matter production and Zn uptake in shoots at low Zn supply . The results demonstrate that although oilseed rape has very small se eds (about 3 mg per seed weight) compared with wheat (30 mg per seed w eight), Zn reserves present in this very small seed still have a stron g impact on early vegetative growth as well as on Zn uptake of plants in Zn-deficient soils. The results suggest that sowing high-Zn seed co upled with growing Zn-efficient genotypes may help in sustaining the p roduction of oilseed rape in Zn-deficient soils, and this has implicat ions for improved seed technology.