Broadley Martin R, Escobar-Gutiérrez Abraham J, Burns Amanda, Burns Ian G
Department of Soil & Environment Sciences, Horticulture Research International, Wellesbourne, Warwick, CV35 9EF, UK.
New Phytol. 2001 Oct;152(1):97-106. doi: 10.1046/j.0028-646x.2001.00240.x.
• C assimilation (A) has been shown to limit the growth of young Lactuca sativa (lettuce) plants following an interruption in their external N supply. Further data from these plants were used to test two hypotheses: that N-limited growth of lettuce is associated with lower stomatal conductance (g ); and that reductions in g result from adjustments to stomatal frequency or distribution. • The photosynthetic characteristics, nitrate and organic N-concentrations, as well as epidermal and stomatal distributions, were determined in leaves of hydroponically grown lettuce plants supplied continuously with N or with N removed for up to 14 d. • Although N-limited plants had lower maximum rates of A, comparisons at equivalent values of g showed that A was not directly limited by organic-N but by g . Reductions in g under N-limiting conditions did not associate with adjustments to stomatal frequency or distribution. • Associations between plant N and A could arise either through stomata responding directly to signals induced by N deprivation or to increased CO partial pressure at the sites of carboxylation.
• 研究表明，在水培生菜（Lactuca sativa）植株的外部氮供应中断后，碳同化作用（A）会限制其生长。利用这些植株的更多数据来检验两个假设：生菜氮素限制生长与较低的气孔导度（g）有关；g的降低是气孔频率或分布调整的结果。
• 测定了水培生菜植株叶片的光合特性、硝酸盐和有机氮浓度，以及表皮和气孔分布，这些植株持续供应氮或去除氮长达14天。
• 尽管氮素限制的植株具有较低的最大A速率，但在g值相等时的比较表明，A并非直接受有机氮限制，而是受g限制。氮素限制条件下g的降低与气孔频率或分布的调整无关。
• 植物氮与A之间的关联可能是通过气孔直接响应氮素剥夺诱导的信号，或者是响应羧化部位二氧化碳分压的增加而产生的。
