Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, 80523, USA.
Department of Horticulture and Landscape Architecture, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, 80523, USA.
Plant Cell Environ. 2019 May;42(5):1561-1574. doi: 10.1111/pce.13511. Epub 2019 Jan 29.
Estimates of seasonal variation in photosynthetic capacity (P ) are critical for modeling the time course of carbon fluxes. Given the time-intensive nature of calculating P parameters via gas exchange, it is appealing to calculate parameter variation via changes in chlorophyll (Chl) and nitrogen (N) content by assuming that P scales with these variables. Although seasonal changes in P and the relationships between N and P have been evaluated in forest canopies, there is limited data on seasonal parameter values in crops, nor is it clear if seasonal changes in P can be estimated from leaf traits under the high N fertility of managed systems. We characterized the seasonal variability of the maximum rates of carboxylation (V ) and electron transport (J ) under well-fertilized conditions for maize (Zea mays L.) and sunflower (Helianthus annuus L.) and coupled these data with measurements of Chl, N, and leaf mass per unit area (LMA). The seasonal Chl-N relationship was significant in maize, but not in sunflower. Area-based N-V relationships were not significant for either crop. Mass-based N-V relationships were weak in sunflower, but highly significant in maize. Our results suggest that P can be seasonally adjusted in maize with reliable estimates of changes in LMA.
对光合作用能力（P）的季节性变化进行估计对于模拟碳通量的时间进程至关重要。鉴于通过气体交换计算 P 参数的性质是密集的，因此通过假设 P 与这些变量成比例来计算参数变化是很有吸引力的，通过改变叶绿素（Chl）和氮（N）含量来计算。尽管已经在森林冠层中评估了 P 的季节性变化以及 N 和 P 之间的关系，但在作物中，关于季节性参数值的数据有限，也不清楚是否可以从管理系统高氮肥力下的叶片特性来估计 P 的季节性变化。我们在良好施肥条件下对玉米（Zea mays L.）和向日葵（Helianthus annuus L.）的羧化（V）和电子传递（J）最大速率的季节性变异性进行了特征描述，并将这些数据与叶绿素、氮和比叶重（LMA）的测量值相结合。在玉米中，季节性 Chl-N 关系显著，但在向日葵中不显著。基于面积的 N-V 关系对两种作物均不显著。基于质量的 N-V 关系在向日葵中较弱，但在玉米中高度显著。我们的结果表明，在玉米中可以根据 LMA 的变化进行可靠的 P 季节性调整。
