In semiarid regions, deficit and unpredictable precipitation results in yield losses. Uniconazole is a plant growth regulator and its application is beneficial in water saving agriculture and improves maize production in semiarid regions. In order to determine the effects of uniconazole application on seed filling and hormonal changes of maize, a field study was conducted in the summer of 2015 and 2016. Seeds were soaked in uniconazole at concentration of 0 (SCK), 25 (S₂₅), 50 (S₅₀), and 75 (S₇₅) mg kg⁻¹, while in the second experiment, uniconazole was applied to the foliage at concentration of 0 (FCK), 25 (F₂₅), 50 (F₅₀), and 75 (F₇₅) mg L⁻¹ at the eight-leaf. Uniconazole application significantly improves the seed filling rates by regulating the endogenous hormones contents. Uniconazole seed soaking treatments improved significantly the seed filling rate of superior, middle, and inferior seeds compared with foliar application treatments. Uniconazole improved significantly the zeatin (Z) + zeatin riboside (ZR) and abscisic acid (ABA) contents while reducing the gibberellic acid (GA) content in the seeds during the process of seed filling. The Z + ZR and ABA contents were significantly positively correlated while the GA content was negatively correlated with maximum seed weight, maximum seed filling rates, and mean seed filling rates. Treatments S₂₅ and F₂₅ significantly improved the above dry matter accumulation plant⁻¹, seed filling rates, ABA, Z + ZR contents, characters of ear, and grain yield while reduced the GA content. It is concluded from our results that the uniconazole application at concentration of 25 mg kg⁻¹ as seed soaking or 25 mg L⁻¹ foliar applied at the eight-leaf stage is beneficial to improve the seed filling rates and grain yield of maize in semiarid regions.

Dark septate endophytes (DSE) are widely distributed in plant roots grown in stressful habitats, especially in heavy metal-polluted soils. But little is known about the physiological interactions between DSE and plants under heavy metal stress. In the present study, the growth, Cd content, and physiological response of Zea mays L. to a root-colonized DSE, Exophiala pisciphila, were analyzed under Cd stress (0, 5, 10, 20, and 40 mg/kg) in a sand culture experiment. Under high Cd (10, 20, and 40 mg/kg) stress, the DSE colonization in roots increased the maize growth, kept more Cd in roots, and decreased Cd content in shoots. The DSE colonization improved the photosynthesis and induced notable changes on phytohormones but had no significant effect on the antioxidant capability in the maize leaves. Moreover, there were significant positive correlations between the gibberellic acid (GA) content and transpiration rate, zeatin riboside (ZR) content, and photosynthetic rate in maize leaves. These results indicated that the DSE’s ability to promote plant growth was related to a decrease on Cd content and the regulation on phytohormone balance and photosynthetic activities in maize leaves.

Abscisic acid (ABA) regulates much important plant physiological and biochemical processes and induces tolerance to different stresses. Here, we studied the regulation of exogenous ABA on adaptation of rice seedlings to simulated acid rain (SAR) stress by measuring biomass dry weight, stomatal conductance, net photosynthesis rate, nutrient elements, and endogenous hormones. The application of 10 μM ABA alleviated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and decreases in contents of nutrient (K, Mg, N, and P) and hormone (auxin, gibberellins, and zeatin). Moreover, 10 μM ABA could stimulate the Ca content as signaling molecules under SAR stress. Contrarily, the application of 100 μM ABA aggravated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and contents of nutrient and hormone. The results got after a 5-day recovery (without SAR) show that exogenous 10 μM ABA can promote self-restoration process in rice whereas 100 μM ABA hindered the restoration by increasing deficiency of nutrients and disturbing the balance of hormones. These results confirmed that exogenous ABA at proper concentration could enhance the tolerance of rice to SAR stress.

Bisphenol A (BPA) is a ubiquitous endocrine-disrupting chemical in the environment that exerts potential harm to plants. Phytohormones play important roles both in regulating multiple aspects of plant growth and in plants’ responses to environmental stresses. But how BPA affects plant growth by regulating endogenous hormones remains poorly understood. Here, we found that treatment with 1.5 mg L⁻¹ BPA improved the growth of soybean seedlings, companied by increases in the contents of indole-3-acetic acid (IAA) and zeatin (ZT), and decreases in the ratios of abscisic acid (ABA)/IAA, ABA/gibberellic acid (GA), ABA/ZT, ethylene (ETH)/GA, ETH/IAA, and ETH/ZT. Treatment with higher concentrations of BPA (from 3 to 96 mg L⁻¹) inhibited the growth of soybean seedlings, meanwhile, decreased the contents of IAA, GA, ZT, and ETH, and increased the content of ABA and the ratios of ABA/IAA, ABA/GA, ABA/ZT, ETH/GA, ETH/IAA, and ETH/ZT. The increases in the ratios of growth and stress hormones were correlated with the increase in the BPA content of the roots. Thus, BPA could affect plant growth through changing the levels of single endogenous hormone and the ratios of growth and stress hormones in the roots because of BPA absorption by the roots.

Conditions of environmental stress are known to lead genetic and epigenetic variability in plants. DNA methylation is one of the important epigenetic mechanisms and plays a critical role in epigenetic control of gene expression. Thus, the aim of the study was to investigate the alteration of genome methylation induced by zinc stress by using coupled restriction enzyme digestion-random amplification (CRED-RA) technique in maize (Zea mays L.) seedlings. In addition, to determine the effect of zinc on mitotic activity and phytohormone level, high-pressure liquid chromatography (HPLC) and mitotic index analysis were utilized. According to the results, mitotic index decreased in all concentrations of zinc except for 5 mM dose and chromosome aberrations such as c-mitosis, stickiness, and anaphase bridges were determined. It was also observed that increasing concentrations of zinc caused an increase in methylation patterns and decrease in gibberellic acid (GA), zeatin (ZA), and indole acetic acid (IAA) levels in contrast to abscisic acid (ABA) level. Especially increasing of ABA levels under zinc stress may be a part of the defense system against heavy metal accumulation in plants.