Search Results (5)

The intra-plant plasticity of leaves plays a vital role in enabling plants to adapt to changing climatic conditions. However, limited research has investigated the extent of intra-plant leaf trait variation and leaf biomass allocation strategies in herbaceous plants. To address this gap, we collected a total of 1746 leaves from 217 Lamium barbatum Siebold and Zucc. plants and measured their leaf dry mass (M) and leaf area (A). Leaves were categorized by vertical position (upper vs. lower canopy layer) and leaf–shoot orientation (east, south, west, north). ANOVA with Tukey’s HSD test was used to compare differences in M, A, and leaf dry mass per unit area (LMA). Reduced major axis regression was employed to evaluate the scaling relationship between M and A, and the bootstrap percentile method was used to determine differences in scaling exponents. The data indicated that: (i) M, A, LMA, and the scaling exponents of M versus A did not differ significantly among leaf–shoot orientations, and (ii) lower layer leaves exhibited significantly greater M, A, and LMA than upper layer leaves, but their scaling exponents were significantly smaller. These findings highlight that plant vertical growth brings significant intra-plant plasticity in leaf traits and their scaling relationships in herbaceous plants. This plasticity differs from that observed in trees, but is also critical for balancing weight load and optimizing light-use efficiency, potentially enhancing stress resilience in herbaceous plants. Full article

Lianas are woody climbing plants and are thought to impact the hosting trees negatively. Ephedra altissima is a liana rising on the Moroccan endemic tree Argania spinosa (L.) Skeels. In this study, our objective was to investigate the impact of the liana on the Argan tree’s physiology and leaf morphology. For that purpose, we compared gas exchange, relative water content, photosynthetic pigment content, and leaf dry mass per unit area of Argan trees associated and not associated with the liana. Our study on individual leaves does not give evidence of the existence or absence of aboveground competition between the liana and the hosting tree. Indeed, photosynthetic rates may suggest that no aboveground competition is occurring. In contrast, pigment content suggests a shading effect of the liana on the hosting tree during the winter season. Otherwise, Argan associated with the liana exhibited a high Chl a/b ratio at the beginning of the dry season, suggesting a belowground competition for nutrient resources. On the other hand, WUEi results indicate that the impact of the liana on the Argan tree may go through seasons with belowground competition for water during spring. The increased LMA values registered in trees associated with the lianasuggest the existence of belowground competition for nutrient resources that persist throughout the year. Full article

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. Full article

Leaf dry mass per unit area (LMA) is considered to represent the photosynthetic capacity, which actually implies a hypothesis that foliar water mass (leaf fresh weight minus leaf dry weight) is proportional to leaf dry weight during leaf growth. However, relevant studies demonstrated that foliar water mass disproportionately increases with increasing leaf dry weight. Although scaling relationships of leaf dry weight vs. leaf area for many plants were investigated, few studies compared the scaling relationship based on leaf dry weight with that based on leaf fresh weight. In this study, we used the data of three families (Lauraceae, Oleaceae, and Poaceae, subfamily Bambusoideae) with five broad-leaved species for each family to examine whether using different measures for leaf biomass (i.e., dry weight and fresh weight) can result in different fitted results for the scaling relationship between leaf biomass and area. Reduced major axis regression was used to fit the log-transformed data of leaf biomass and area, and the bootstrap percentile method was used to test the significance of the difference between the estimate of the scaling exponent of leaf dry weight vs. area and that of leaf fresh weight vs. area. We found that there were five species across three families (Phoebe sheareri (Hemsl.) Gamble, Forsythia viridissima Lindl., Osmanthus fragrans Lour., Chimonobambusa sichuanensis (T.P. Yi) T.H. Wen, and Hibanobambusa tranquillans f. shiroshima H. Okamura) whose estimates of the scaling exponent of leaf dry weight to area and that of leaf fresh weight to area were not significantly different, whereas, for the remaining ten species, both estimates were significantly different. For the species in the same family whose leaf shape is narrow (i.e., a low ratio of leaf width to length) the estimates of two scaling exponents are prone to having a significant difference. There is also an allometric relationship between leaf dry weight and fresh weight, which means that foliar water mass disproportionately increases with increased leaf dry weight. In addition, the goodness of fit for the scaling relationship of leaf fresh weight vs. area is better than that for leaf dry weight vs. area, which suggests that leaf fresh mass might be more able to reflect the physiological functions of leaves associated with photosynthesis and respiration than leaf dry mass. The above conclusions are based on 15 broad-leaved species, although we believe that those conclusions may be potentially extended to other plants with broad and flat leaves. Full article

Longleaf pine has been classified as very shade intolerant but leaf physiological plasticity to light is not well understood, especially given longleaf pine’s persistent seedling grass stage. We examined leaf morphological and physiological responses to light in one-year-old grass-stage seedlings and young trees ranging in height from 4.6 m to 6.3 m to test the hypothesis that young longleaf pine would demonstrate leaf phenotypic plasticity to light environment. Seedlings were grown in a greenhouse under ambient levels of photosynthetically active radiation (PAR) or a 50% reduction in ambient PAR and whole branches of trees were shaded to provide a 50% reduction in ambient PAR. In seedlings, shading reduced leaf mass per unit area (LMA), the light compensation point, and leaf dark respiration (R_D), and increased the ratio of light-saturated photosynthesis to R_D and chlorophyll b and total chlorophyll expressed per unit leaf dry weight. In trees, shading reduced LMA, increased chlorophyll a, chlorophyll b and total chlorophyll on a leaf dry weight basis, and increased allocation of total foliar nitrogen to chlorophyll nitrogen. Changes in leaf morphological and physiological traits indicate a degree of shade tolerance that may have implications for even and uneven-aged management of longleaf pine. Full article