Drought-Tolerant Barley: II. Root Tip characteristics in Emerging Roots

Abstract

Reduced water resources are of increasingly urgent global concern. One potential strategy to address the crisis is the use of drought tolerant crops in agriculture. Barley varieties developed for reduced irrigation (“Solum” and “Solar”) use significantly less water than conventional varieties (“Cochise” and “Kopious”). The underlying mechanism of this drought tolerance is unknown but root structure and function play a key role in plant water uptake. In this study, an empirical survey compared early root development between drought tolerant and conventional varieties. Traits associated with root meristem-regulated cell division including rate of seed germination, border cell number and root cap mucilage production, and root hair emergence were quantified during root emergence. Preliminary results revealed that drought tolerant varieties exhibited faster seed germination and root hair production than conventional varieties. Border cell number and mucilage production in the drought tolerant varieties also were higher than in the conventional variety “Kopious,” but lower than in “Cochise”. Each trait, if found to be linked to the observed drought tolerance, could yield a simple, rapid, and inexpensive tool to screen for new crop varieties. Further detailed studies are needed.

Soil, climate, and variety impact on quantity and quality of maize root mucilage exudation

“…As mucilage plays important roles in maize water uptake under water stress (Ahmed et al 2018), it is therefore plausible that plant breeders in Kenya unintentionally selected for higher mucilage exudation, while selecting for drought resistance. Carter et al (2019) also indicated a higher mucilage exudation amount in a droughtresistant barley (Hordeum vulgare L.) compared to the drought-susceptible ones, suggesting a similar selection effect.…”

“…It was recently shown that the amount of nodal root mucilage exudation in the drought-resistant maize (Z. mays L.) varieties from India and Kenya were significantly higher than in those from Germany and France, being positively associated with the vapor pressure deficit of the varieties' agroecological zones of origin (Nazari et al 2020). Moreover, mucilage exudation was higher in a drought-resistant barley (Hordeum vulgare L.) variety than a conventional one (Carter et al 2019). These studies postulate that higher amounts of mucilage exudation have been unintentionally selected in the course of breeding under drought conditions.…”

Variability in seed germination of barley cultivars (Hordeum vulgare L.) grown under different nitrogen application rates

“…The functioning of connection gene hormones is related to germination response, which can be reduced under stress conditions (salt, drought) in sensitive barley cultivars (Emre et al, 2011;Thabet et al, 2018), and the physiological damage to the seed caused by stress can negatively affect seed viability and vigour, depending on genotype (Sun et al, 2007). In addition, the dynamic nature of root tip properties could have a significant impact on drought tolerance (Carter et al, 2019). Also, under salinity stress conditions, barley seed treatment with tryptophan and ascorbic acid as magneto-priming can improve seed germination (Hozayn and Ahmed, 2019).…”

Black Poplar (Populus nigra L.) Root Extracellular Trap, Structural and Molecular Remodeling in Response to Osmotic Stress

“…Nazari et al [ 40 ] studied the composition and quantity of mucilage exuded by maize from contrasting climatic regions and found that Indian and Kenyan genotypes from semi-arid regions secreted 135 and 125% more mucilage, respectively, compared to genotypes from central Europe. Similarly, India ink staining showed that root tips of drought-tolerant barley genotypes produced 1.2- to 1.5-times more mucilage than sensitive genotypes [ 39 ]. In addition, the secretion of mucilage provides both a biofilm-like environment and an accessible carbon source, which could help maintain beneficial microbial communities in the rhizosphere during a drought [ 87 , 88 ].…”

“…It is hypothesized that the mucilage acts as a hydraulic bridge between the roots and the soil, facilitating plant water uptake and maintaining transpiration in dry soils [ 6 ]. Most studies have focused on a range of grassland or crop species with different growth strategies [ 37 ], such as chickpea [ 38 ], barley [ 39 ], or maize [ 40 ].…”