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Open AccessArticle

Effects of Salt Stress on the Leaf Shape and Scaling of Pyrus betulifolia Bunge

1
Bamboo Research Institute, College of Biology and the Environment, Nanjing Forestry University, Nanjing 210037, China
2
Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland 7602, South Africa
3
Mathematical and Physical Biosciences, African Institute for Mathematical Sciences, Cape Town 7945, South Africa
*
Author to whom correspondence should be addressed.
Symmetry 2019, 11(8), 991; https://doi.org/10.3390/sym11080991
Received: 20 June 2019 / Revised: 24 July 2019 / Accepted: 29 July 2019 / Published: 2 August 2019
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Abstract

Leaf shape can reflect the survival and development of plants in different environments. In particular, leaf area, showing a scaling relationship with other leaf-shape indices, has been used to evaluate the extent of salt stress on plants. Based on the scaling relationships between leaf area and other leaf-shape indices in experiments at different levels of salt stress, we could examine which leaf-shape indices are also related to salt stress. In the present study, we explored the effects of different salt concentration treatments on leaf dry mass per unit area (LMA), the quotient of leaf perimeter and leaf area (QPA), the quotient of leaf width and length (QWL), the areal quotient (AQ) of left and right sides of a leaf and the standardized index (SI) for bilateral symmetry. We treated Pyrus betulifolia Bunge under NaCl salt solution of 2‰, 4‰ and 6‰, respectively, with fresh water with no salt as the control. The reduced major axis (RMA) was used to fit a linear relationship of the log-transformed data between any leaf trait measures and leaf area. We found that leaf fresh weight and dry weight decrease with salt concentration increasing, whereas the exponents of leaf dry weight versus leaf area exhibit an increasing trend, which implies that the leaves expanding in higher salt environments are prone to have a higher cost of dry mass investment to increase per unit leaf area than those in lower salt environments. Salt concentration has a significant influence on leaf shape especially QWL, and QWL under 6‰ concentration treatment is significantly greater than the other treatments. However, there is no a single increasing or decreasing trend for the extent of leaf bilateral symmetry with salt concentration increasing. In addition, we found that the scaling exponents of QPA versus leaf area for four treatments have no significant difference. It indicates that the scaling relationship of leaf perimeter versus leaf area did not change with salt concentration increasing. The present study suggests that salt stress can change leaf functional traits especially the scaling relationship of leaf dry weight versus leaf area and QWL, however, it does not significantly affect the scaling relationships between leaf morphological measures (including QPA and the extent of leaf bilateral symmetry) and leaf area. View Full-Text
Keywords: areal quotient of the left and right sides of a leaf; leaf area; leaf bilateral symmetry; leaf dry mass; salt damage areal quotient of the left and right sides of a leaf; leaf area; leaf bilateral symmetry; leaf dry mass; salt damage
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Yu, X.; Shi, P.; Hui, C.; Miao, L.; Liu, C.; Zhang, Q.; Feng, C. Effects of Salt Stress on the Leaf Shape and Scaling of Pyrus betulifolia Bunge. Symmetry 2019, 11, 991.

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