Abstract
Drought is a common natural disaster in barley production, which restricts the growth and development of barley roots and caryopses seriously, thereby decreasing yield and debasing grain quality. However, mechanisms for how drought stress affects barley caryopses and roots development under drought stress are unclear. In this paper, Suluomai1 was treated with drought from flowering to caryopses mature stage. The morphological and structural changes in roots growth and caryopses development of barley were investigated. Drought stress increased root/shoot ratio and eventually led to the 20.16% reduction of ear weight and 7.75% reduction of 1,000-grain weight by affecting the biomass accumulation of roots and caryopses. The barley roots under drought had more lateral roots while the vessel number and volume of roots decreased. Meanwhile, drought stress accelerated the maturation of caryopses, resulting in a decrease in the accumulation of starch but a significant increase of protein accumulation in barley endosperm. There was a significantly positive correlation (0.76) between the area of root vessel and the relative area of protein in endosperm cells under normal condition and drought increased the correlation coefficient (0.81). Transcriptome analysis indicated that drought induced differential expressions of genes in caryopses were mainly involved in encoding storage proteins and protein synthesis pathways. In general, drought caused changes in the morphology and structure of barley roots, and the roots conveyed stress signals to caryopses, inducing differential expression of genes related to protein biosynthesis, ultimately leading to the increase in the accumulation of endosperm protein. The results not only deepen the study on drought mechanism of barley, but also provide theoretical basis for molecular breeding, high-yield cultivation and quality improvement in barley.
Highlights
Barley (Hordeum vulgare L.) is an important food, feed and cash crop, and its planting area ranks fourth all around the world (Lü, Wu & Fu, 2015)
drought stress (DS) promoted the precocity of caryopses and affected the substance accumulation in caryopses with a decrease in endosperm starch but an increase in endosperm protein
The changes of roots structure caused by DS had a greater influence on the accumulation of endosperm protein
Summary
Barley (Hordeum vulgare L.) is an important food, feed and cash crop, and its planting area ranks fourth all around the world (Lü, Wu & Fu, 2015). Novel insights into the effect of drought stress on the development of root and caryopsis in barley. Previous studies have found that barley roots can absorb inorganic salt and water and transport them to the aboveground parts (Varney & Canny, 1993; Xiong et al, 2006), so the roots morphological characteristics can be used as a key index for drought tolerance evaluation (Chloupek et al, 2010). Previous researches pointed that drought reduced the number of tillers, plant height and grains per ear of barley, resulting in a significant decrease in thousand kernel weight and yield of the ear (Samarah, 2005; Samarah et al, 2009). Studies showed that protein content in grains increased, starch content and size changed, while starch structure did not change significantly under drought stress (Nezhadahmadi, Prodhan & Faruq, 2013; Gous, Gilbert & Fox, 2015; Yu et al, 2017). The discovery of drought-tolerant genes and their quantitative trait loci are of great significance to the breeding and quality improvement of barley (Nevo & Chen, 2010)
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