Allocation Mechanisms of Non-Structural Carbohydrates of Robinia pseudoacacia L. Seedlings in Response to Drought and Waterlogging

Abstract

Climate change is likely to lead to an increased frequency of droughts and floods, both of which are implicated in large-scale carbon allocation and tree mortality worldwide. Non-structural carbohydrates (NSCs) play an important role in tree survival under stress, but how NSC allocation changes in response to drought or waterlogging is still unclear. We measured soluble sugars (SS) and starch in leaves, twigs, stems and roots of Robinia pseudoacacia L. seedlings that had been subjected to a gradient in soil water availability from extreme drought to waterlogged conditions for a period of 30 days. Starch concentrations decreased and SS concentrations increased in tissues of R. pseudoacacia seedlings, such that the ratio of SS to starch showed a progressive increase under both drought and waterlogging stress. The strength of the response is asymmetric, with the largest increase occurring under extreme drought. While the increase in SS concentration in response to extreme drought is the largest in roots, the increase in the ratio of SS to starch is the largest in leaves. Individual components of SS showed different responses to drought and waterlogging across tissues: glucose concentrations increased significantly with drought in all tissues but showed little response to waterlogging in twigs and stems; sucrose and fructose concentrations showed marked increases in leaves and roots in response to drought but a greater response to drought and waterlogging in stems and twigs. These changes are broadly compatible with the roles of individual SS under conditions of water stress. While it is important to consider the role of NSC in buffering trees against mortality under stress, modelling this behaviour is unlikely to be successful unless it accounts for different responses within organs and the type of stress involved.

Combined Effects of Drought and Shading on Growth and Non-Structural Carbohydrates in Pinus massoniana Lamb. Seedlings

“…Under drought conditions, the ratio of soluble sugar to starch remained relatively stable, except for the increase observed in branches, and both soluble sugar and starch increased slightly. However, this result contrasts with previous studies which have reported that the ratio of soluble sugar to starch significantly increased [25], and the increase in soluble sugars was converted to starch [64]. This may have been due to the inhibition of growth and metabolism being much greater than photosynthesis rate in our study, which would result in the accumulation of starch in all organs.…”

“…Our findings will be helpful in predicting the impact of climate change on P. massoniana growth.Non-structural carbohydrate (NSC), a carbon reserve for energy and biosynthesis, provides energy for physiological processes (e.g., metabolism, cell turgor maintenance, and embolism repair) [21,22] and plant growth [23]. Plants enriched with higher NSC concentrations can maintain metabolic functions for survival and long-term growth [22,24,25], and their resistance to stressful environments is increased [26]. Both drought and shading cause an imbalance in organic carbon supply and demand that results in a trade-off between plant growth and NSC storage [27][28][29][30][31], which in turn affects plant growth and stress tolerance [32,33].…”

Seed Germination and Seedling Growth of Robinia pseudoacacia Depending on the Origin of Different Geographic Provenances

“…After harvesting, seeds were labeled for each provenance and deposited in paper bags in a refrigerator (at approximately +4 • C) until further analysis. Moreover, since water stress is known to induce both morphological and anatomical changes [50][51][52], seedlings were also studied [53]. The seedlings obtained from treated seeds were further analysed by being kept in the laboratory for three months, then taken outside in natural conditions; at the end of six months, morphological traits were measured: height, stem diameter and number of branches.…”

Disentangling the Effects of Tree and Soil Properties on the Water Uptake of a Waterlogging Tolerant Tree in the Yangtze River Delta, China

“…Changes in global precipitation increase the frequency and intensity of extreme precipitation in humid areas, subsequently leading to frequent floods [1][2][3]. Floods induced by extreme precipitation expose trees to waterlogging stress, and cause root hypoxia and inhibit plant respiration, ultimately increasing the tree mortality [4][5][6]. This phenomenon is particularly universal in the river basins and estuarine deltas of tropical/subtropical areas [7][8][9].…”