The Analysis of Petiole Histological Traits Through an Evaluation of Water Deficit Tolerance of Sugar Beet Genotypes

Water stress is considered as one of the most widespread limitations to sugar beet productivity and yield stability. Since leaf is the most significantly affected organ by drought, we focused on the petiole histological features of ten sugar beet genotypes that previously showed divergent responses to lack of water in the field. The aim was to calculate volume densities of petiole different tissues and determine the histological sources of the genotypic differences in the breeding material with respect to water use efficiency. Comparative histological analysis of the petiole was performed using classic anatomical (proximal and distal segments) and stereological methods. The plants were grown in semi-controlled glasshouse conditions. The general structure of the sample variability was established by Principal component analysis, based on the correlation matrix data. This study suggests that determination of the variation in the histological characteristics of the petioles can play an important role in water management in plants. The results reveal a higher level of variability in morphometric parameters due to the fact that petiole cross-section shapes change with its maturity. Characteristics, such as (i) petiole shape, (ii) arrangement and number of vascular bundles, (iii) number and size of vessels, (iv) volume density and distribution of collenchyma, and (v) volume density of parenchyma are promising criteria that can help in the selection of more drought tolerant genotypes.