Analysis of Classic Tomato Mutants Reveals Influence of Leaf Vein Density on Fruit BRIX

Tomato bipinnate (bip) is a classic leaf mutant, with highly increased leaf complexity resulting from the loss of function of a BEL-LIKE HOMEODAMAIN (BELL) gene. Here, we analyzed several bip mutants and their isogenic wildtype backgrounds for a suite of leaf morphology traits, ranging from leaf complexity, leaflet shape and size, to leaf vascular density to investigate how changes in leaf morphology influence fruit traits. Our analyses showed an unexpected relationship between leaf vein density and fruit sugar levels, where leaf vein density was negatively correlated with fruit BRIX. RNA-Seq analysis suggested variation in Glucose-6-phosphate translocator2 (GPT2) gene expression caused correlated changes in leaf vein density and BRIX when bip mutant and wildtype were compared, suggesting that the correlation between leaf vein density and fruit sugar may result from the genes regulating leaf vein development that are also involved in regulating leaf sugar biosynthesis. Our results provide a resource for further exploration of the genetic basis for the complex relationship between fruit quality and leaf traits in natural populations.

Leaf Vein Density of Tree Saplings Composing Lower Canopy in Tropical Forest Reflects Their Ecophysiological Characteristics

One factor affecting the survival of a species in a tropical ecosystem is its ability to respond to environmental conditions, which depend on their ecophysiological performances. Plants ability to transport water as a major environmental factor would determine their survival. The anatomy of xylem inside leaves and stem as water conductive tissue will dictate the rate of water transport through the plant stem and leaves. Leaf vein, which contains xylem vessels, dictates water transport through leaves and plant’s ability to control water loss through stomata. This research found that tree saplings composing a lower canopy of tropical forests have different ecophysiological attributes. Pioneer species, such as Cinnamomum sp., Diospyros macrophylla, Castanopsis costata, Elateriospermum tapos, and Ziziphus sp., have higher leaf vein density than primary species, such as a member of genus Garcinia, Shorea, Dipterocarpus, and Syzigium. It implies that pioneer species might have higher rates of water transport and consequently, higher rates of photosynthesis. If forest vegetation was more opened, then pioneer species may dominate the area as they are more tolerant of light. The Composition of forest vegetation with different ecophysiological characteristics may affect the forest dynamics and hydrological cycle.

Leaf and Stem Traits are Linked to Liana Growth Rate in a Subtropical Cloud Forest

There is accumulating evidence that the abundance and biomass of lianas are increasing with global climate change in the Neotropics. However, our knowledge of growth–trait relationships among lianas is surprisingly rare. Here, we monitored the relative growth rate of 2860 individuals from seven deciduous and four evergreen liana species in a 20 ha subtropical cloud forest dynamics plot at high elevation (2472–2628 m a.s.l.) in southwest China. We linked the relative growth rate of lianas with nine leaf traits associated with leaf morphology, nutrient concentrations, and water hydraulic capacity as indicated by leaf vein density, and five stem wood traits related to stem water transport capacity and wood density. Our results showed that deciduous lianas have higher relative growth rates than their evergreen counterparts. Across all lianas studied, the relative growth rate was positively correlated with the leaf area and specific leaf area, but negatively correlated with leaf dry matter content. The relative growth rate of lianas was strongly correlated with nitrogen concentration after excluding the legume liana species. The relative growth rate was decoupled from leaf phosphorus and potassium concentrations, leaf vein density, and stem vessel traits across all lianas investigated. For four evergreen lianas, there were positive associations of the relative growth rate with the leaf thickness and diameter of the largest vessels. This study is the first to illustrate the relationships of liana growth with leaf and stem traits in the high-elevation subtropical cloud forest. More studies from diverse forest ecosystems are needed to comprehensively understand the mechanism underlying liana growth patterns.

Identification of Venation Type Based on Venation Density using Digital Image Processing

Leaf venation is one biometric feature of leaves that have an important role in growth processes of the plant, and to determine the relationship of the plant physiology and the environment in which plants grow. At every different environment, plants have different types of leaf venation. It can be seen from the level of the leaf vein density. In this study, the feature of leaf vein density was used to identify the leaves based on venation type. The venation density features obtained from segmentation, vein detection, and density feature extraction of leaf venation. Identification of the venation type was made using the artificial neural network (ANN). The results of this study indicate that the proposed method can classify the leaf correctly image based on the venation type. On the dataset with 324 samples, the accuracy of 82.71% was obtained. This shows that the leaf vein density features allow use as a plant identifier.Keywords: leaf vein density, vein detection, density feature extraction, artificial neural network

Elevated auxin biosynthesis and transport underlie high vein density in C4 leaves

High vein density, a distinctive trait of C4 leaves, is central to both C3-to-C4 evolution and conversion of C3 to C4-like crops. We tested the hypothesis that high vein density in C4 leaves is due to elevated auxin biosynthesis and transport in developing leaves. Up-regulation of genes in auxin biosynthesis pathways and higher auxin content were found in developing C4 leaves compared with developing C3 leaves. The same observation held for maize foliar (C4) and husk (C3) leaf primordia. Moreover, auxin content and vein density were increased in loss-of-function mutants of Arabidopsis MYC2, a suppressor of auxin biosynthesis. Treatment with an auxin biosynthesis inhibitor or an auxin transport inhibitor led to much fewer veins in new leaves. Finally, both Arabidopsis thaliana auxin efflux transporter pin1 and influx transporter lax2 mutants showed reduced vein numbers. Thus, development of high leaf vein density requires elevated auxin biosynthesis and transport.

Leaf vein density and photosynthetic rate in Rosa: Is there a correlation?

A thorough knowledge of the leaf vascular network and its evolution is essential for understanding the fluid dynamics of water movement in leaves. Recent studies have shown how these networks can be involved in the performance of photosynthesis, which is linked to the density of the vascular network per unit of leaf area. The aim of this study is to highlight the correlation between leaf vein density (VD) and physiological parameters. The hypothesis proposed was tested on the leaves ofthe “Isabel Renaissance” (IR) rose cultivar. The main result concerned the VD, which was significantly correlated with the maximum leaf net photosynthetic rate (PN). This finding supports the hypothesis that the vascular system of IR leaves can be correlated with leaf photosynthesis performance.