Contrasting leaf intercellular space development in sorghum and maize modulates different tolerance capacity to water limitation.

The objective of this study was to evaluate the relationship between intercellular spaces and leaf gas exchange and the effect of total intercellular space on the growth of maize and sorghum under water restriction. The experiments were conducted in a greenhouse in a 2 × 3 factorial arrangement (two plant types and three water conditions: field capacity (FC = 100%), 75%FC, and 50%FC) with 10 replicates. The lack of water was a limiting factor for maize because it showed reductions in leaf area, leaf thickness, biomass, and gas exchange parameters, while sorghum remained unchanged, maintaining its water-use efficiency. This maintenance was correlated with the growth of intercellular spaces in sorghum leaves because the increased internal volume led to better CO2 control and prevented excessive water loss under drought stress. In addition, sorghum had more stomata than maize. These characteristics contributed to the drought tolerance of sorghum, while maize could not make the same adjustments. Therefore, changes in intercellular spaces promoted adjustments to avoid water loss and may have improved CO2 diffusion, characteristics that are important for drought-tolerant plants.

Root anatomy, growth, and development of Typha domingensis Pers. (Typhaceae) and their relationship with cadmium absorption, accumulation, and tolerance.

Typha domingensis Pers. is a plant that grows in marshy environments, where cadmium (Cd) accumulates. The root is the first organ that comes into contact with the metal. The aim of this study was to evaluate the effect of Cd on the roots of T. domingensis. The experiment was conducted in a greenhouse using different Cd concentrations: (1) 0 µM (control), (2) 10 µM, and (3) 50 µM, with 10 replicates for 90 days. The plants were placed in plastic containers containing 5 L of nutrient solution modified with the different Cd concentrations. At the end of the experiment, the roots were measured, sampled, fixed, and subjected to usual plant microtechniques. The slides were observed and photographed under light microscopy and analyzed in ImageJ software. To measure Cd absorption, atomic-absorption spectrometry was used. The data were subjected to analysis of variance and comparison of means by the Scott-Knott test at P < 0.05. When exposed to 50 µM of Cd, the roots accumulated 99.35% of the Cd. At this concentration, there was a reduction in the exodermis but there was an increase in the diameter of the cortical cells and in the proportion of aerenchyma in the cortex. There was an increase in the root cap, which guaranteed the protection of the primary meristems. Therefore, T. domingensis adjusts its root anatomy improving the Cd tolerance and shows potential for phytoremediation purposes.

Stomatal cavity modulates the gas exchange of Sorghum bicolor (L.) Moench. grown under different water levels.

This work aimed to evaluate the effects of lower water levels on leaf intercellular spaces and to assess their relations with the gas exchange, anatomy, and growth of Sorghum bicolor. Experiments were conducted in a greenhouse, in which plants were subjected to three water conditions (ten replicates, n = 30): well-irrigated, decreased irrigation, and limited irrigation. Lower water levels had no significant effect on the growth of S. bicolor but increased the biomass of the roots. Moreover, the number of leaves, leaf area, and leaf size as well as the chlorophyll content were not affected by lower water levels, and no significant changes were detected for whole plant photosynthesis, transpiration, or stomatal conductance. The water content of the plants and the water potential remained unchanged. However, compared with other treatments, the decreased irrigation decreased water loss and increased the water retention. Lower water levels increased the intercellular CO2 percentage, mesophyll area, and proportion of stomatal cavities and promoted minor changes in leaf tissue and stomatal traits. The increased stomatal cavities provided higher CO2 uptake and prevented excessive water loss. Thus, modifications to the intercellular spaces promoted conditions to avoid excessive water loss while concurrently improving CO2 uptake, which are important traits for drought-tolerant plants.

Leaf ontogeny of Schinus molle L. plants under cadmium contamination: the meristematic origin of leaf structural changes.

Previous works show the development of thicker leaves on tolerant plants growing under cadmium (Cd2+) contamination. The aim of this study was to evaluate the Cd2+ effects on the leaf meristems of the tolerant species Schinus molle. Plants were grown in nutrient solution containing 0, 10, and 50 µM of Cd2+. Anatomical analysis was performed on leaf primordia sampled at regular time intervals. Under the lowest Cd2+ level (10 µM), increased ground meristem thickness, diameter of the cells, cell elongation rate, and leaf dry mass were found. However, 50 µM of Cd2+ reduced all these variables. In addition, the ground meristem cells became larger when exposed to any Cd2+ level. The epidermis, palisade parenchyma, and vascular tissues developed earlier in Cd2+-exposed leaves. The modifications found on the ground meristem may be related to the development of thicker leaves on S. molle plants exposed to low Cd2+ levels. Furthermore, older leaves showed higher Cd2+ content when compared to the younger ones, preventing the Cd2+ toxicity to these leaves. Thus, low Cd2+ concentrations change the ground meristem structure and function reflecting on the development of thicker and enhanced leaves.