The Physiological Role of Abscisic Acid in Regulating Root System Architecture of Alfalfa in Its Adaptation to Water Deficit

Abstract

Alfalfa (Medicago sativa L.) is a perennial leguminous plant, with a strong tap root system that plays an important role in alfalfa’s adaptation to drought stress. However, a better understanding of root functional traits and how these root traits are related to whole plant responses in order to improve pasture productivity under water deficit. Two greenhouse experiments were conducted: Experiment 1 used three alfalfa cultivars and four levels of soil water content treatments to investigate herbage productivity, growth point density, residual shoot weight, and root weight. Experiment 2 assessed relationships among root-sourced abscisic acid (ABA), root system architecture and plant biomass in response to water deficit. The results demonstrated that root system was used as a useful tool to improve tolerant and adaptation when alfalfa copied with lower levels of soil water content. On average, maintaining 60–65% soil water-holding capacity alfalfa had the highest herbage accumulation (6.7 g DM pot-1), growing point density (46.5 pot-1), and residual shoot biomass (1.8 g DM pot-1). At the level of water stress, Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) tended to exhibit a herringbone branching pattern with less root tips, root forks, altitude, and magnitude than cv Golden empress (GE). Principal component analysis and structural equation modeling revealed that root-sourced ABA positively regulated the altitude and magnitude of root system architecture, root tips and root forks, and was closely associated with plant root biomass and herbage biomass. It was concluded that these findings can contribute to developing optimum irrigation strategies and help alfalfa breeders in the development of new cultivars with improved drought tolerance based on root system architecture, plant hormone, and plant growth.

Combined Transcriptomics and Metabolomics Analysis Reveals Profenofos-Induced Invisible Injury in Pakchoi (Brassica rapa L.) through Inhibition of Carotenoid Accumulation

“…The abscisic acid (ABA) content of 10 g of each leaf sample was extracted using an acetonitrile solution containing 1% acetic acid; after centrifugation and purification, the supernatant was collected and analyzed by liquid chromatography−tandem mass spectrometry analysis (Xevo TQ-S; Waters, Milford, MA, USA) (instrument conditions and the limit of quantification are shown in Text S5). 36 2.12. Quantitative Reverse Transcription−Polymerase Chain Reaction Analysis.…”

Metabolomics reveal root differential metabolites of different root-type alfalfa under drought stress

“…Alfalfa (or Lucerne) ( Medicago sativa L.), as a high-protein legume and more drought-resistant than other forage, is extensively grown in semi-arid and arid regions of China ( Nan et al., 2019 ; Li et al., 2022 ), but still the growing drought poses a main threat to alfalfa acreage and output ( Wu et al., 2017 ; Wasaya et al., 2021 ). Therefore, improving the water use efficiency and drought-resistance breeding of alfalfa are the keys to increasing alfalfa yield.…”

Transcriptome analysis reveals candidate genes for different root types of alfalfa in response to drought stress

“…Many DEGs involved in alfalfa's drought response are linked to numerous stress processes, such as sugar metabolism, lignin, and wax biosynthesis [4]. Genes associated with abscisic acid metabolism, root growth, antioxidant enzyme activity, cell membrane stability, ubiquitination, and genetic processing all respond to drought stress [24][25][26], and DEGs expression patterns involved in the abscisic acid and auxin hormone signaling pathways have been found to change under stress in numerous studies [27][28]. Research has shown that alfalfa circular RNA (circRNA) and long non-coding RNA (lncRNA) exhibit diversity under drought and high salt stress, which may be key node genes regulating stress [29].…”