ABSTRACT.
Changes in elastic modulus, leaf tensity and leaf density during dehydration of detached leaves in two plant species of Moraceae

Deke Xing1*, 3, Xiaole Chen1, Yanyou Wu2, Zhenyi Li1, and Shanjida Khan3
 
The quick adjustments of leaf traits are critical for keeping the survival of plants under dehydration. In this study, we examined the hypotheses that plants would adapt to dehydration by shrinking its mesophyll cells to offset the water loss, or triggering water regulation mechanism caused by enzymes. Leaf structure, elasticmodulus (Em), leaf tensity (LT) and leaf density (LD) were determined with detached leaves of Broussonetia papyrifera (L.) Vent. and Morusalba L. at each water loss moment (0, 1, 2, 3, 4 and 5 h). The coupling model between gripping force and LT was established using the Gibbs free energy equation, and the initial LT was determined. The intracellular water availability of M. albadecreased at 4h, which was earlier than that of B. papyrifera. The intracellular water availability of M. alba was more sensitive than B. papyrifera. Broussonetia papyrifera adapted to dehydration by shrinking its mesophyll cells to offset the water loss, or triggering water regulation mechanism caused by enzymes, i.e., carbonic anhydrase. The sponge parenchyma of B. papyrifera at 3 h decreased by 25.73% of that at control. Morus alba maintained intracellular water availability just by changing the leaf structure. The offset effects through shrinking cells differed between B. papyrifera and M. alba, because the elastic-plastic behavior of their leaves and cells were different. The Em of M. alba was over five-fold higher than that of B. papyrifera . The investigations of water status were more accurate in terms of leaf physical traits instead of water content.
Keywords: Anatomical structure, Broussonetia papyrifera, cell volume, leaf tensity, mechanical strength, Morus alba, water translocation.
1Jiangsu University, Key Laboratory of Modern Agricultural Equipment and Technology, Ministry of Education, Institute of Agricultural Engineering, 212013, Zhenjiang, P.R. China. *Corresponding author (xingdeke@ujs.edu.cn).
2Research Center for Environmental Bio-Science and Technology, State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081, Guiyang, P.R. China.
3University of Alberta, Department of Renewable Resources, Edmonton, AB, T6G 2E3, Canada.