Retta Moges, Yin Xinyou, van der Putten Peter E L, Cantre Denis, Berghuijs Herman N C, Ho Quang Tri, Verboven Pieter, Struik Paul C, Nicolaï Bart M
BIOSYST-MeBioS, KU Leuven/Flanders Center of Postharvest Technology, Willem de Croylaan 42, B-3001 Leuven, Belgium; Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands.
Centre for Crop Systems Analysis, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands; BioSolar Cells, P.O. Box 98, 6700 AB Wageningen, The Netherlands.
Plant Sci. 2016 Nov;252:205-214. doi: 10.1016/j.plantsci.2016.07.013. Epub 2016 Jul 25.
The mechanism of photosynthesis in C crops depends on the archetypal Kranz-anatomy. To examine how the leaf anatomy, as altered by nitrogen supply and leaf age, affects the bundle sheath conductance (g), maize (Zea mays L.) plants were grown under three contrasting nitrogen levels. Combined gas exchange and chlorophyll fluorescence measurements were done on fully grown leaves at two leaf ages. The measured data were analysed using a biochemical model of C photosynthesis to estimate g. The leaf microstructure and ultrastructure were quantified using images obtained from micro-computed tomography and microscopy. There was a strong positive correlation between g and leaf nitrogen content (LNC) while old leaves had lower g than young leaves. Leaf thickness, bundle sheath cell wall thickness and surface area of bundle sheath cells per unit leaf area (S) correlated well with g although they were not significantly affected by LNC. As a result, the increase of g with LNC was little explained by the alteration of leaf anatomy. In contrast, the combined effect of LNC and leaf age on S was responsible for differences in g between young leaves and old leaves. Future investigations should consider changes at the level of plasmodesmata and membranes along the CO leakage pathway to unravel LNC and age effects further.
C4作物的光合作用机制取决于典型的花环结构。为了研究氮供应和叶龄改变后的叶片解剖结构如何影响维管束鞘导度（g）, 在三种不同的氮水平下种植了玉米（Zea mays L.）植株。对两个叶龄的完全成熟叶片进行了气体交换和叶绿素荧光联合测量。使用C4光合作用的生化模型分析测量数据以估算g。利用从微计算机断层扫描和显微镜获得的图像对叶片微观结构和超微结构进行了量化。g与叶片氮含量（LNC）之间存在很强的正相关关系，而老叶的g低于幼叶。叶厚度、维管束鞘细胞壁厚度和单位叶面积维管束鞘细胞的表面积（S）与g相关性良好，尽管它们不受LNC显著影响。因此，g随LNC的增加几乎无法用叶片解剖结构的改变来解释。相反，LNC和叶龄对S的综合作用导致了幼叶和老叶之间g的差异。未来的研究应考虑沿着CO2泄漏途径在胞间连丝和膜水平上的变化，以进一步阐明LNC和叶龄的影响。
