Grain legumes differ in nitrogen accumulation and remobilisation during seed filling |
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| Authors: | Silvia Pampana Alessandro Masoni Iduna Arduini |
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| Institution: | Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124 Pisa, Italy |
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| Abstract: | In grain legumes, the N requirements of growing seeds are generally greater than biological nitrogen fixation (BNF) and soil N uptake during seed filling, so that the N previously accumulated in the vegetative tissues needs to be redistributed in order to provide N to the seeds. Chickpea, field bean, pea, and white lupin were harvested at flowering and maturity to compare the relative contribution of BNF, soil N uptake, and N remobilisation to seed N. From flowering to maturity, shoot dry weight increased in all crops by approximately 50%, root did not appreciably change, and nodule decreased by 18%. The amount of plant N increased in all crops, however in field bean (17?g?m?2) it was about twice that in chickpea, pea, and lupin. The increase was entirely due to seeds, whose N content at maturity was 26?g?m?2 in field bean and 16?g?m?2 in chickpea, pea, and lupin. The seed N content at maturity was higher than total N accumulation during grain filling in all crops, and endogenous N previously accumulated in vegetative parts was remobilised to fulfil the N demand of filling seeds. Nitrogen remobilisation ranged from 7?g?m?2 in chickpea to 9?g?m?2 in field bean, and was crucial in providing N to the seeds of chickpea, pea, and lupin (half of seed N content) but it was less important in field bean (one-third). All the vegetative organs of the plants underwent N remobilisation: shoots contributed to the N supply of seeds from 58% to 85%, roots from 11% to 37%, and nodules less than 8%. Improving grain legume yield requires either reduced N remobilisation or enhanced N supply, thus, a useful strategy is to select cultivars with high post-anthesis N2 fixation or add mineral N at flowering. |
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| Keywords: | Biological nitrogen fixation chickpea field bean pea nitrogen remobilisation white lupin |
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