Mining anatomical traits: a novel modelling approach for increased water use efficiency under drought conditions in plants

Abstract

Crop yields are reduced by 70–80% due to a water stress situation specifically during the reproductive stage and are not able to fulfil the needs of food requirement in developed and developing countries of the world. Earlier work was mainly focused on the use of morphological or physiological and molecular aspects for improved stress tolerance. Efforts are being made to overcome this problem with the help of today’s sophisticated and advanced technology through genomics, proteomics and metabolomics. The presented model summarizes our work in the last five years to mine anatomical parameters as a novel approach to further improving introgression or exploitation of stress adaptive traits. We have focused on some key anatomical traits playing a substantial role in water stress tolerance. This new conceptual model encompasses increased palisade mesophyll height, higher leaf strength index (LSI), higher number of conducting tissues with increased diameter in leaf, stem and root and controlled transpiration rate due to a lower number of stomata per unit leaf area along with the increased guard cell size. Different plants viz. Lycopersicon esculentum, Capsicum annuum, and Calotropis gigantea were screened by developing polyploids to validate this model approach. Genotypes of Vitis vinifera and Solanum melongena were also screened. Wild relatives like Lycopersicon esculentum var. cerasiforme and Solanum khasianum were evaluated for comparison. These observations were further correlated with various stress adaptation traits like yield under stress, in vitro screening, chlorophyll content, transpiration heating and cooling, molecular markers etc. A new scoring method is proposed which will be helpful to screen a large set of germplasms on a preliminary basis to discriminate genotypes for drought tolerance. There is an urgent need to study the genetics of these stress adaptive traits using high throughput molecular markers to make them more useful for a higher magnitude of genetic gain.

Evaluating drought resistant wheat cultivars based on stem anatomical characteristics

“…During this study (Figure 2), maximum epidermal thickness was reported from the genotypes 21 and 25 respectively ( Figure 15U, Figure 15Y) whereas other cultivars were not showing any significant differences in the thickness of epidermal cells. Results are in accordance with the findings of Kulkarni et al (2008) those have reported higher epidermal cell size in xerophytes plants.…”

“…Secondary phloem was found with higher width in drought resistant cultivars stem and this increased the ability of conducting more food material (Kulkarni & Deshpande 2006). Further, Kulkarni et al (2008) suggested that higher proportion of phloem and conducting tissues in stem were positively correlated with dry matter production under stress conditions .…”

“…Among the texted 25 wheat accessions, minimum stem width was reported from the wheat genotype 3, 17 and 22 ( Figure 10C, Figure 14Q, Figure 15V). According to Kulkarni et al (2008) this increase in photosynthetically active stem tissues across the section is an index of increase drought resistance. Further, it was believed that the increased in the amount of photosynthetic parenchyma may increase the water use efficiency of plants under a water stress situation (Kulkarni et al, 2008).…”

“…Bigger vascular bundles can improve the stem efficiency under drought stress conditions. According to Kulkarni et al (2008) higher number of vessels in stem increases the efficiency of translocation along with conductivity and photosynthetic storage which can impart adaptability to drought stress. Blum (2011) discussed genotypic variation for the ability to store and mobilizes carbohydrates for seed filling during terminal moisture stress.…”

“…Kulkarni et al (2008) reported that drought susceptible genotypes of tomato had smaller and less number of xylem vessels whereas resistant genotypes have more xylem vessels with bigger size. On the other hand increasing the xylem diameter in some plant may also beneficial under water stress condition and provide a water reservoir to the plants which used at day times when water demand is high ( Martre & Durand, 2001, Abbasi et al, 2016.…”