Effect of boron supply on the uptake of micronutrients by radish (raphanus sativus l.)

摘要

The present study was based on the hypothesis that Boron (B) induces changes of other micronutrients in soil-plant systems. A preliminary study was carried out in sand culture growing radish (cv. French breakfast) as a test crop, under green house conditions. The experiment was laid out in a randomized complete block design and replicated three times. Boron was applied at the rate of 0, 0.25, 0.50, 1.0, 2.0, 3.0 and 5.0 mg B L-1as H3BO3 along with a basal dose of modified complete nutrient solution based on the Long Ashton Formula. Results revealed that significant treatment effects were found on the growth response of radish plants, and maximum yield was recorded at 0.5 mg L-1 of added B. Toxic effects accompanied by considerable yield decreases was observed at higher levels of B supply. The concentrations of B, Zn and Cu in plants were increased and Fe, Mn and Mo were decreased. The total uptake of all micronutrients except B decreased with increasing levels of B in the nutrient solution, and showed close similarity to the growth response of radish plants. Generally, low and high levels of added B had interactive effects on the concentration and total uptake of micronutrients. Moreover, Zn/Cu ratio increased and Mn/Zn and Mn/Fe decreased, while Fe/Cu showed inconsistent trend with increasing B levels in the nutrient solution. Differences in the concentration and total uptake of micronutrients occurred because of (a) nutrient concentration or dilution in the radish plants, and (b) nutrient distribution among the root and top of plants. Differences arising purely from differential distribution could be eliminated if the composition of the entire plant is considered as a unit. It was however, evident that B supply had specific effects with respect to different micronutrients.