China Agricultural University, College of Resources and Environmental Sciences, Beijing, China.
Wageningen University, Centre for Crop Systems Analysis, Droevendaalsesteeg, the Netherlands.
Ann Bot. 2018 Apr 18;121(5):1005-1017. doi: 10.1093/aob/mcx210.
Within-plant spatial heterogeneity in the production of and demand for assimilates may have major implications for the formation of fruits. Spatial heterogeneity is related to organ age, but also to position on the plant. This study quantifies the variation in local carbohydrate availability for the phytomers in the same cohort using a cotton growth model that captures carbohydrate production in phytomers and carbohydrate movement between phytomers.
Based on field observations, we developed a functional-structural plant model of cotton that simulates production and storage of carbohydrates in individual phytomers and transport of surplus to other phytomers. Simulated total leaf area, total above-ground dry mass, dry mass distribution along the stem, and dry mass allocation fractions to each organ at the plant level were compared with field observations for plants grown at different densities. The distribution of local carbohydrate availability throughout the plant was characterized and a sensitivity analysis was conducted regarding the value of the carbohydrate transport coefficient.
The model reproduced cotton leaf expansion and dry mass allocation across plant densities adequately. Individual leaf area was underestimated at very high plant densities. Best correspondence with measured plant traits was obtained for a value of the transport coefficient of 0.1 d-1. The simulated translocation of carbohydrates agreed well with results from C-labelling studies. Moreover, simulation results revealed the heterogeneous pattern of local carbohydrate availability over the plant as an emergent model property.
This modelling study shows how heterogeneity in local carbohydrate production within the plant structure in combination with limitations in transport result in heterogeneous satisfaction of demand over the plant. This model provides a tool to explore phenomena in cotton that are thought to be determined by local carbohydrate availability, such as branching pattern and fruit abortion in relation to climate and crop management.
植物体内同化物的产生和需求的空间异质性可能对果实的形成产生重大影响。空间异质性与器官年龄有关，但也与植物的位置有关。本研究使用棉花生长模型量化了同一生长期内植物各部分局部碳水化合物供应的变化，该模型捕获了植物各部分的碳水化合物生产和碳水化合物在植物各部分之间的移动。
基于田间观测，我们开发了一种棉花的功能结构植物模型，该模型模拟了单个植物各部分碳水化合物的生产和储存以及向其他植物各部分的过剩转移。模拟的总叶面积、总地上干物质、茎干沿茎的干物质分布以及植物水平上每个器官的干物质分配分数与在不同密度下生长的植物的田间观测值进行了比较。对整个植物的局部碳水化合物供应分布进行了特征描述，并对碳水化合物运输系数的值进行了敏感性分析。
该模型在不同密度下对棉花叶片扩展和干物质分配的模拟结果较好。在非常高的植物密度下，单个叶片面积被低估。当运输系数值为 0.1 d-1 时，模型与测量的植物特征的拟合度最佳。模拟的碳水化合物转运与 C 标记研究的结果吻合较好。此外，模拟结果揭示了植物体内局部碳水化合物供应的异质性模式，这是一种新兴的模型特性。
这项模拟研究表明，植物结构内局部碳水化合物生产的异质性与转运的限制相结合，导致了植物整体上需求的不均匀满足。该模型为探索棉花中被认为由局部碳水化合物供应决定的现象提供了一种工具，例如与气候和作物管理有关的分枝模式和果实败育。
