Contributions of Root WSC during Grain Filling in Wheat under Drought

Abstract

As the first organ in plants to sense water-deficit in the soil, roots have important roles for improving crop adaption to water limited environments. Stem water soluble carbohydrates (WSC) are a major carbon source for grain filling under drought conditions. The contributions of root WSC during grain filling under drought has not been revealed. Wheat parental lines of Westonia, Kauz and their derived four double haploid (DH) lines, namely, DH 125, DH 139, DH 307, and DH 338 were used in a field drought experiment with four replications. Through measurements of the root and stem WSC components, and the associated enzyme activities during grain filling, we identified that the levels of root WSC and fructan were one third of the levels in stems. In particular, root glucose and 6-kestose levels were one third of the stem, while the root fructose and bifurcose level were almost half of the stem and sucrose level was two third of the stem. The accumulation and the degradation patterns of root fructan levels were similar to that in the stem, especially under drought. Correlations between root fructan levels and grain assimilation were highly significant, indicating that under terminal drought, root WSC represents a redistributed carbon source for grain filling rather than deep rooting. The significantly higher root sucrose levels under drought suggest that sucrose may act as a signal under drought stress. As compared with stem fructose levels, the earlier increased root fructose levels in DH 307, DH 139, and DH 338 provided agile response to drought stress. Our root results further confirmed that β-(2–6) linkages predominate in wheat with patterns of 6-kestose being closely correlated with overall fructan patterns. Further research will focus on the roles of 6-FEH during fructan remobilization in stems.

Diurnal Changes in Water Soluble Carbohydrate Components in Leaves and Sucrose Associated TaSUT1 Gene Expression during Grain Development in Wheat

“…In agreement with previous research on Kauz and Westonia [9], a major component of the plant WSC is stored in the stem. In the current study, the WSC level in stems is double that in the leaves, and the accumulation of stem WSC is mainly based on the increment in fructan concentrations in the stems (82% of stem WSC).…”

“…The major phenotypic contributors to wheat grain yield are thousand grain weight (TGW) and kernel number per spike (KN) [2][3][4]. The sum of glucose, fructose, sucrose and fructans, hereafter termed "water soluble carbohydrate" (WSC) in wheat stems and leaf sheaths is one of the crucial parameters contributing to grain yield especially under terminal drought conditions [5][6][7][8][9]. Interestingly, the remobilization of stem WSC is subject of considerable genetic variation, and molecular marker screening has been useful in identifying suitable lines for pre-breeding [7].…”

“…So far, leaves have been the main focus to study carbohydrate dynamics in a diurnal context. Although dynamic fluxes of wheat stem and root WSC components have been investigated throughout the period of wheat grain filling [8,9], to the best of our knowledge no studies have been performed yet to study the carbohydrate dynamics in these organs in a diurnal context. Here, we aim to fill this knowledge gap in the context of wheat grain filling.…”

Effects of Drought Stress on Growth and Development of Wheat Seedlings

“…According to the Food and Agriculture Organization of the United Nations, Human farming, grazing took possession of 25-30%. Humans cannot effectively use the remaining dry land for plant production (Hu and Xiong, 2014;Zhang et al, 2016). Thus, it is urgent to clarify effect of drought stress on growth and development of wheat.…”

Higher activity of monodehydroascorbate reductase and lower activities of leaf and spike vacuolar invertase and glutathione S-transferase reveals higher number of grains per spike in spring wheat genotypes grown under well-watered and drought conditions

“…Likewise the activity of adenosine diphosphate-glucose pyrophosphorylase (AGPase) is associated with grain filling [29] and under drought conditions an increased activity of AGPase within the grains of wheat and rice was reported by Yang et al [14]and Zhang et al [30]. Under drought stress, translocation of limited carbohydrates from source tissues to grains [31] and; from sink tissues to grains is important to determine the grain yield under stress [32]. Li et al [33] reported an increase in the activity of spike phosphoglucomutase and aldolase under high CO 2 indicating the role carbohydrate metabolism within spike in response to an enhanced source activity.…”