Wheat (Triticum aestivum L.) grain filling and dry matter partitioning responses to source:sink modifications under postanthesis water and nitrogen deficiency = Enchimento de gr os de trigo (Triticum aestivum L.) e respostas da parti o de mat谷ria seca 角s modifica es fonte:dreno sob defici那ncia de 芍gua e nitrog那nio ap車s a antese

作者：Ahad Madani; Amirhossein Shirani Rad; Alireza Pazoki; Ghorban Nourmohammadi

来源：Acta Scientiarum - Agronomy, 2010.

• current photosynthesis
• dry matter allocation
• grain filling rate
• stem reserves
• wheat (Triticum aestivum L.)
• fotossintese corrente
• aloca o de materia seca
• taxa de enchimento de gr os
• reservas do colmo
• trigo

Re-translocation of stem and spike reserves was investigated in source:sink restricted wheat subjected to water and nitrogen deficiency during seed filling. Either sink or source restriction significantly decreased the amount of current photosynthesis and itscontribution to grain yield. Furthermore, source limitation increased stem and spike reserves contribution to seed filling process. Higher amount of stem reserve mobilization in source restricted vs. control and sink restricted plants indicates that at rapid grain filling stage (14 days after anthesis to physiological maturity), stem dry matter decreases to provide assimilates for kernel after defoliation. In spike halved plants, drought stress significantly decreased grain yield, indicating that when the sink is restricted, postanthesis drought stress can increase sink limitation through lower grain filling rate and dry matter allocation to grain two weeks after anthesis at the beginning of rapid grain filling stage. On the other hand, in spike halved plants, more nitrogen supply at anthesis increased grain yield because more dry matter allocation to grain is not associated with more current photosynthesis. But when all the leaves were removed except flag leaf, more postanthesis nitrogen could not increase dry matter allocation to grain filling process,showing that postanthesis nitrogen supply increases grain yield by decreasing sink limitation, and not by increasing source strength. A retransloca o de reservas do colmo e espiga foi investigada com rela o 角s restri es de fonte e dreno em plantas submetidas 角 defici那ncia de 芍gua e nitrog那nio durante o enchimento de gr os. A fotoss赤ntese e a sua contribui o para a produtividade foram reduzidas por ambas restri es. As restri es na fonte aumentaram a contribui o das reservas do colmo e da espiga. A maior mobiliza o de fonte sob restri o versus o controle e o dreno sob restri o indica que, no per赤odo de maior enchimento, a mat谷ria seca do colmo foi reduzida por fornecer os assimilados ap車s a restri o. Nas espigas reduzidas, a produtividade foi afetada pelo estresse h赤drico indicando que ap車s a antese o estresse pode aumentar a limita o por causa de taxas mais altas de enchimento e transloca o de mat谷ria seca duas semanas ap車s a antese. Nas espigas reduzidas, o maior fornecimento de nitrog那nio durante a antese elevou a produtividade porque maior transloca o de mat谷ria seca n o est芍 associada 角 maior fotoss赤ntese. O n赤vel mais alto de nitrog那nio n o foi capaz de aumentar a transloca o quando todas as folhas, exceto a bandeira,foram removida