Increase in Absolute Leaf Water Content Tends to Keep Pace with That of Leaf Dry Mass—Evidence from Bamboo Plants

Abstract

Leaves, as the most important photosynthetic organ of plants, are intimately associated with plant function and adaptation to environmental changes. The scaling relationship of the leaf dry mass (or the fresh mass) vs. leaf surface area has been referred to as “diminishing returns”, suggesting that the leaf area fails to increase in proportion to leaf dry mass (or fresh mass). However, previous studies used materials across different families, and there is lack of studies testing whether leaf fresh mass is proportional to the leaf dry mass for the species in the same family, and examining the influence of the scaling of leaf dry mass vs. fresh mass on two kinds of diminishing returns based on leaf dry mass and fresh mass. Bamboo plants (Poaceae: Bambusoideae) are good materials for doing such a study, which have astonishingly similar leaf shapes across species. Bamboo leaves have a typical parallel venation pattern. In general, a parallel venation pattern tends to produce a more stable symmetrical leaf shape than the pinnate and palmate venation patterns. The symmetrical parallel veins enable leaves to more regularly hold water, which is more likely to result in a proportional relationship between the leaf dry mass and absolute water content, which consequently determines whether the scaling exponent of the leaf dry mass vs. area is significantly different from (or the same as) that of the leaf fresh mass vs. area. In the present study, we used the data of 101 bamboo species, cultivars, forms and varieties (referred to as 101 (bamboo) taxa below for convenience) to analyze the scaling relationships between the leaf dry mass and area, and between leaf fresh mass and area. We found that the confidence intervals of the scaling exponents of the leaf fresh mass vs. dry mass of 68 out of the 101 taxa included unity, which indicates that for most bamboo species (67.3%), the increase in leaf water mass keeps pace with that of leaf dry mass. There was a significant scaling relationship between either leaf dry mass or fresh mass, and the leaf surface area for each studied species. We found that there was no significant difference between the scaling exponent of the leaf dry mass vs. leaf area and that of the leaf fresh mass vs. leaf area when the leaf dry mass was proportional to the leaf fresh mass. The goodness of fit to the linearized scaling relationship of the leaf fresh mass vs. area was better than that of the leaf dry mass vs. area for each of the 101 bamboo taxa. In addition, there were significant differences in the normalized constants of the leaf dry mass vs. fresh mass among the taxa (i.e., the differences in leaf water content), which implies the difference in the adaptabilities to different environments across the taxa.

“Diminishing returns” for leaves of five age‐groups of Phyllostachys edulis culms

“…The data for the DM vs. A scaling relationship exhibits the phenomenon of diminishing returns (when DM is exactly or approximately proportional to FM), whereas the scaling relationship between DM and A has been shown to be statistically weaker compared to that between FM and A (Huang et al, 2019a(Huang et al, , 2019b(Huang et al, , 2020Liu et al, 2020). Consequently, the available data indicate that FM appears to be a better measure of leaf functional traits compared to DM (Kramer and Boyer, 1995), although this may not be the case for evergreen species (see Athokpam et al, 2014).…”

“…Most of the studies dealing with diminishing returns are focused Am J Bot. 2021;108:1662-1672. wileyonlinelibrary.com/journal/AJB 1662 | © 2021 Botanical Society of America on comparing the numerical values of α across different plant life-forms and across different types of communities (Milla and Reich, 2007;Niklas et al, 2007;Li et al, 2008;Zhu et al, 2019;Shi et al, 2020a), the influence of abiotic and abiotic factors on the numerical values of α (Niklas and Cobb, 2008;Niklas and Christianson, 2011;Pan et al, 2013;Sun et al, 2017;Thakur et al, 2019;Yu et al, 2019;Lin et al, 2020;Liu et al, 2020), and the difference between the numerical values of the scaling exponent of leaf dry mass vs. area and those of leaf fresh mass vs. area (Huang et al, 2019a(Huang et al, , 2019b(Huang et al, , 2020.…”

“…It is important to note, however, that the majority of these studies have drawn on data primarily from eudicot species. A notable exception is the study of Huang et al (2020) who reported that the scaling relationships between leaf dry mass and area of 101 bamboo species, cultivars, forms, and varieties and 83 bamboo taxa follow the law of diminishing returns.…”

“…Lin et al (2020) report that the ratio of leaf width to leaf length can significantly affect the scaling exponent. Huang et al (2019aHuang et al ( , 2019bHuang et al ( , 2020 found that the scaling relationship between leaf fresh mass (FM) and area is stronger than that between leaf dry mass (DM) and A, and that the scaling exponent of FM vs. A is often numerically smaller than that of DM vs. A. Another potentially important factor, which has not been adequately explored, is the effect of plant age.…”

Application of an Ovate Leaf Shape Model to Evaluate Leaf Bilateral Asymmetry and Calculate Lamina Centroid Location

“…The leaf is crucial to the growth and development of plants, with the characteristics and variation of leaf structure directly affecting absorption and utilization of light energy and nutrients ( Smith et al, 1997 ; Daas-Ghrib et al, 2011 ). Previous studies have shown that there is a tradeoff between the photosynthetic returns from increasing lamina area and the investment in leaf physical support and hydraulic systems from increasing lamina mass ( Niklas et al, 2007 ; Huang et al, 2019a , b , 2020 ; Guo et al, 2021 ). Lamina thickness and leaf shape have been demonstrated to affect such a tradeoff ( Niinemets et al, 2007 ; Lin et al, 2018 , 2020 ).…”