Increase in absolute leaf water content tends to keep pace with that of leaf dry mass - Evidence from bamboo plants

Authors: HUANG, WEIWEI - NANJING FORESTRY UNIVERSITY; Reddy, Gadi V.P.; LI, YUEYI - NANJING FORESTRY UNIVERSITY; LARSEN, JORGEN BO - UNIVERSITY OF COPENHAGEN; SHI, PEIJIAN - UNIVERSITY OF GOTTINGEN

Submitted to: Symmetry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2020
Publication Date: 8/12/2020
Citation: Huang, W., Reddy, G.V., Li, Y., Larsen, J., Shi, P. 2020. Increase in absolute leaf water content tends to keep pace with that of leaf dry mass - Evidence from bamboo plants. Symmetry. 12, 1345. https://doi.org/10.3390/sym12081345.
DOI: https://doi.org/10.3390/sym12081345

Interpretive Summary: The leaf area and leaf dry mass could represent the balance between the investment in growth and that in storage and could be used to predict the growth strategy and response to environmental variations for leaves. Our previous studies have found this same allometric relationship between leaf dry mass and leaf surface area for five Lauraceae, five Oleaceae, eight Rosaceae, ten climbing species and seventeen bamboo species. Leaf water content is associated with leaf area increases. In current study, we examined 10,045 leaves from 101 bamboo taxa from 17 genera, aiming to determine (i) whether leaf fresh mass was proportional to leaf dry mass, or if there was an allometric relationship, and what proportion of species showed a proportional or allometric relationship; (ii) what proportion of species showed “diminishing returns” referring to the scaling relationship between leaf fresh/dry mass and leaf surface area; (iii) and whether majority of the studied bamboo species exhibited a better scaling relationship between leaf fresh mass vs. leaf surface area rather than leaf dry mass vs. leaf surface area. Current study increases our understanding of the scaling relationships between leaf fresh mass and leaf dry mass, and between leaf mass and leaf surface area of bamboo. The influence of leaf vascular architectures (e.g., venation style, vein density, vein diameter, etc.) on the relationship between leaf water mass and leaf dry mass, as well as that between leaf fresh mass and area, merits further investigation.

Technical Abstract: Foliar is the most important component of a plant’s photosynthetic apparatus and plays a pivotal role in plant function and long-time adaptation to environmental change. The scaling relationship of leaf dry mass (or fresh mass) vs. leaf surface area has been referred to as “diminishing returns” suggesting that leaf area fail to increase in proportion to leaf dry mass (or fresh mass). However, previous studies used materials across different families, and there is lack of study to test whether leaf fresh mass is proportional to leaf dry mass for the species in the same family and to examine 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 research, 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 leaf dry mass and absolute water content, which consequently determines whether the scaling exponent of leaf dry mass vs. area is significantly different from (or the same as) that of leaf fresh mass vs. area. In the present study, we used the data 31 of 101 bamboo species, cultivars, forms and varieties (referred to as 101 (bamboo) taxa below for convenience) to analyze the scaling relationships between leaf dry mass and area and between leaf fresh mass and area. We found that the confidence intervals of the scaling exponents of 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 of 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 leaf surface area for each studied species. We found that there was no significant difference between the scaling exponent of leaf dry mass vs. leaf area and that of leaf fresh mass vs. leaf area when leaf dry mass 39 was proportional to leaf fresh mass. The goodness of fit to the linearized scaling relationship of leaf fresh mass vs. area was better than that of leaf dry mass vs. area for each of the 101 bamboo taxa. In addition, there were significant differences in the normalized constants of 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.