Inoculation of Azospirillum brasilense and exogenous application of trans-zeatin riboside alleviates arsenic induced physiological damages in wheat (Triticum aestivum).

Due to increased industrialization, arsenic (As) in the soil has become a serious issue for wheat production since past few decades. We investigated the role of Azospirillum brasilense and trans-zeatin riboside (tZR) in the mitigation of arsenic toxicity in wheat for 2 years (2018-2019 and 2019-2020) in pot experiments. Wheat plants grown in soil artificially spiked with arsenic (50, 70, and 100 µM) was left alone or amended with A. brasilense, tZR, or their combination as mitigation strategies. A treatment without arsenic or amendments was maintained as control. Arsenic-induced physiological damages were noticed in the wheat plants. Detrimental effects on the plant physiological functions, such as disruption of cell membrane stability, reduced water uptake, and stomatal functions, were noticed with increase in As toxicity. Application of biological amendments reversed the effects of As toxicity by increasing wheat plant growth rate, leaf area, and photosynthesis and also yield. Therefore, application of tZR and wheat seed inoculation with A. brasilense could be a sustainable and environmentally friendly strategy to mitigate arsenic-induced crop physiological damages.

Endogenous hormonal equilibrium linked to bamboo culm development.

Moso bamboo (Phyllostachys heterocycla) is the most important bamboo species in China and is famous for its fast-growing culms. To investigate the possible relationship between internode development and endogenous hormones, the concentrations of indole-3-acetic acid (IAA), zeatin riboside (ZR), gibberellins (GA3), and abscisic acid (ABA) were analyzed in culm samples from plants at different developmental stages during a single growing season and, at the same time, anatomical structure was closely monitored. Cell division was the dominant process in internode development during early development, while cell elongation predominated at later stages. There was a negative correlation between the rates of cell division and cell elongation. The four endogenous hormones (IAA, ZR, GA3, and ABA) displayed fluctuations in their levels at different developmental stages but their peak activities were not synchronous. Cell division rate had a significant positive correlation with ZR concentration. Cell elongation had a significant positive correlation with the ratio of promoting hormones (IAA, GA3, and ZR) to inhibitory hormone (ABA) concentrations. We conclude that hormonal equilibrium might regulate the division and elongation of bamboo culms.

Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris).

Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al-drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the alleviation of Al toxicity by osmotic stress (-0.60 MPa polyethylene glycol) in hydroponics. However, drought reduced the impact of Al on the root tip, as indicated by the reduction of Al-induced callose formation and MATE expression. Combined Al and drought stress enhanced up-regulation of ACCO expression and synthesis of zeatin riboside, reduced drought-enhanced abscisic acid (ABA) concentration, and expression of NCED involved in ABA biosynthesis and the transcription factors bZIP and MYB, thus affecting the regulation of ABA-dependent genes (SUS, PvLEA18, KS-DHN, and LTP) in root tips. The results provide circumstantial evidence that in soil, drought alleviates Al injury, but Al renders the root apex more drought-sensitive, particularly by impacting the gene regulatory network involved in ABA signal transduction and cross-talk with other phytohormones necessary for maintaining root growth under drought.

Thidiazuron influences the endogenous levels of cytokinins and IAA during the flowering of isolated shoots of Dendrobium.

This study reports the effects of thidiazuron (TDZ) on the endogenous levels of indoleacetic acid (IAA), zeatin, zeatin riboside ([9R]Z), isopentenyladenine and isopentenyladenosine ([9R]iP) as well as structural changes in the apical meristem of Dendrobium Second Love shoots during flower induction and initial development in vitro. The results revealed that the presence of 1.8microM TDZ had a profound effect on the endogenous cytokinins (CKs) and IAA levels of the explants, when compared to those grown on a TDZ-free medium. A significant increase in CKs (especially [9R]iP and [9R]Z) and IAA in the first samples (taken at day 5) grown on TDZ-enriched medium was associated with flower induction, while a second increase in the level of these hormones after 25d of culture was related to flower development. The histological changes detected in the shoot apical meristem of explants grown in the presence of 1.8microM TDZ during 30d of culture are also described. Based on these findings, it is suggested that both auxin and CKs seem to be involved with the floral transition of Dendrobium Second Love in vitro. However, a possible direct effect of TDZ on flower formation is not discarded.