Plant Size Plays an Important Role in Plant Responses to Low Water Availability and Defoliation in Two Woody Leguminosae Species

Abstract

Plant size influences plant responses to combined environmental factors under climate change. However, their roles in plant ecophysiological responses are not fully understood. Two rapidly growing Leguminosae species (Robinia pseudoacacia and Amorpha fruticosa) were used to examine plant responses to combined drought and defoliation treatments (two levels of both treatments). Both 1.5 month-old seedlings and 3 month-old seedlings were grown in a greenhouse, and seedling growth, leaf gas exchanges, stem hydraulics, and concentrations of non-structural carbohydrates were determined after 60 days of treatment. Our results indicated defoliation had no significant effect on plant height, basal diameter, and total biomass whatever plant sizes and species. Under the low water availability treatment, the defoliated seedlings significantly increased by 24% in stem water potential compared with non-defoliated seedlings in large R. pseudoacacia. Compared with the high water availability in large non-defoliated R. pseudoacacia seedlings, the low water availability significantly reduced by 26% in stem starch concentration to maintain the stem soluble sugar concentration stable, but not in small R. pseudoacacia seedlings. We also found a negative correlation between leaf and root soluble sugar concentration under low water availability in A. fruticosa. The results demonstrate defoliation could relieve the effect of low water availability in large seedlings. Large seedlings had more compensatory mechanisms in response to defoliation and drought treatments than small seedlings, thus species with large carbon reserves are more recommended for vegetation restoration under combined drought and defoliation conditions. Future studies with more species are crucial for obtaining more rigorous conclusions.

Seasonal decline in leaf photosynthesis in perennial switchgrass explained by sink limitations and water deficit

“…The late summer photosynthetic decline may be driven by sink limitations triggered by rhizome carbohydrate buildup. As perennial grass biomass allocation to flowers and seeds is minimal ( Boe, 2007 ; Giannoulis et al., 2016 ), mature stands may lack major sinks for photosynthates once vegetative growth has ceased ( Tejera et al., 2021 ; Tejera et al., 2022 ) and rhizome carbohydrate accumulation is complete. Rhizome carbohydrate concentrations and leaf photosynthesis were inversely correlated, and as rhizome starch reached maximum accumulation in mid-summer, leaf photosynthesis declined to low rates ( Figures 1 , 5 ).…”

“…Perennial grasses notably increase in size during the growing season, with larger plants being progressively more susceptible to water limitation as a larger transpiring leaf area increases total water demand and increasingly depletes available soil water (Liu et al, 2016;Mocko and Jones, 2021;Wang et al, 2021). Therefore, the observed photosynthetic decline could be a consequence of water limitation as plants become larger and soil water becomes less available later in the growing season.…”

“…The late-season photosynthesis decline could also be driven by co-occurring physiological changes. Specifically, physiological signals like carbohydrate buildup and sink strength are known to limit development and leaf photosynthesis in certain perennial grasses ( McCormick et al, 2009 ; Van Heerden et al., 2010 ; De Souza et al., 2018 ; Ruiz-Vera et al., 2021 ; Tejera et al., 2021 ; Tejera et al., 2022 ) . For example, when the photoassimilate source-sink balance was perturbed by shading some leaves of sugarcane plants, photosynthesis in the unshaded leaves increased by 32%, indicating source-sink coordination at the level of the entire plant to match supply (source) with demand (sinks) ( McCormick et al, 2006 ).…”

Screening of Tetraploid Wheat Genotypes for Drought Tolerance during Early Growth Stage by Multivariate Analysis and Stress Indices

“…However, among all the stresses affected by climate change, drought is the main factor restricting plant production (Cohen et al 2021). More speci cally, the effects of drought stress on plants gradually increase (Wang et al 2021). Climate change is foreseen to constitute progressively severe and extensive drought terms in the following 30-90 years, as weather heat increases, affecting much of the earth, including of the world's top food-producing areas.…”

Physiological Responses of Robinia pseudoacacia and Quercus acutissima Seedlings to Repeated Drought-Rewatering Under Different Planting Methods

“…Moreover, on the “isohydric-anisohydric” continuous spectrum, R. pseudoacacia is an anisohydric species, while Q. acutissima is an isohydric one ( Wang and Zhou, 2000 ; Li et al, 2020 ). Besides, there are many seedlings in the regeneration layer under forests ( Wang et al, 2021 ). The regeneration of woody plant seedlings is an important component of maintaining the vegetation diversity of forest ecosystem ( Fukushima et al, 2008 ), playing a central role in the process of community assembly and forest dynamic changes ( Nyland et al, 2006 ).…”