EEFECT OF BORON ON GROWTH NODULATION AND NITROGEN FIXATION OF SOYBEAN NODULATING MUTANTS AND ITS PARENT CV. BRAGG——I. GROWTH, MINERAL COMPOSITION AND TOTAL AMOUNT OF NITROGEN FIXATION

This study was undertaken to detertunins how boron might affect the growth, mineral composition, nodulation and nitrogen fixation in short term hydroponically cultured soybean nodulating mutants (nts382, nod49) and its parent cv. Bragg in N-free solution. The results show that total plant biotnass, plant height and primary root length of nonnqdulating mutant (nod49) were more than those of supernodulating mutant or its parent cv. Bragg in normal boron supply culture (5.0gmol L-1B) respectively. The root biomass of supernodulating mutant was the lest in three soybean genotypes in both boron treatments. The growth of three soybean genotypes was severely inhibited in non -boron supply treatment. Both nts382 nitrogen concentration and accumulation in each plant part in normal boron supply treatment were more than those in nonboror treatment and nts 382 root nodules exhibited high N2-fixing capacity in both treatments. Nitrogen fixation of Bragg root nodules was severely inhibited and nts382 was less inhibited and still remained high N2-fixing capacity in campari-son with Bragg in non-boron culture. Boron supply increased boron concentration and accumulation in each plant part and decreased calcium concentration and accumulation in both root and nodules of Bragg and nts382. Whereas, Mo concentration and accumulation increased in nts 382 nodules but Fe, Mn, Cu, Zn contents decreased in normal boron treatment.