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Strigolactones (SLs) are a class of plant hormones and rhizosphere communication signals of great interest. They perform diverse biological functions including the stimulation of parasitic seed germination and phytohormonal activity. However, their practical use is limited by their low abundance and complex structure, which requires simpler SL analogues and mimics with maintained biological function. Here, new, hybrid-type SL mimics were designed, derived from Cinnamic amide, a new potential plant growth regulator with good germination and rooting-promoting activities. Bioassay results indicated that compound 6 not only displayed good germination activity against the parasitic weed O. aegyptiaca with an EC50 value of 2.36 × 10−8 M, but also exhibited significant inhibitory activity against Arabidopsis root growth and lateral root formation, as well as promoting root hair elongation, similar to the action of GR24. Further morphological experiments on Arabidopsis max2-1 mutants revealed that 6 possessed SL-like physiological functions. Furthermore, molecular docking studies indicated that the binding mode of 6 was similar to that of GR24 in the active site of OsD14. This work provides valuable clues for the discovery of novel SL mimics. [ABSTRACT FROM AUTHOR]

Aims: In this study, a novel plant growth regulator 2,4-dichloroformamide cyclopropane acid (B2) was used to explore its effects on wheat stalk morphology, chemical composition, anatomical structure, crushing strength and their relationship with lodging resistance. The effects of stem quality change on grain filling and yield were further discussed. Methods: We conducted a series of experiments, including determinations of internode morphology and breaking resistance, analyses of chemical composition and hormone content, observation of internode anatomy, and measurement of grain filling rate, to explore the effects of internode developmental changes induced by B2 treatment on grain filling. Results: Spraying 150 μmol·L−1 B2 at jointing stage significantly decreased plant height, height of center of gravity, basal internode and cell length, while increased stem diameter, wall thickness of basal second internode, cortex thickness, vascular bundle transverse section area and cell cross-sectional area, which resulted in higher breaking strength and culm lodging resistance index. B2 also significantly reduced the content of gibberellin in the second basal internode, and increased the accumulation of lignin and cellulose, thus forming a shorter and stronger stalk. Correlation analysis showed that stem outer diameter, stem wall thickness, cellulose and lignin content were significantly and positively correlated with stem breaking strength. The improvement of stalk structure, especially vascular bundle area, increased bleeding sap, which contributed to grain filling and final yield formation. Conclusions: Lodging resistance and average grain-filling rate can be enhanced by spraying B2 at wheat jointing stage due to the improvement of culm structure, which is conducive to further increase of yield. [ABSTRACT FROM AUTHOR]

Salt stress negatively affects maize growth and yield. Application of plant growth regulator is an effective way to improve crop salt tolerance, therefore reducing yield loss by salt stress. Here, we used a novel plant growth regulator B2, which is a functional analogue of ABA. With the aim to determine whether B2 alleviates salt stress on maize, we studied its function under hydroponic conditions. When the second leaf was fully developed, it was pretreated with 100 µM ABA, 0.01 µM B2, 0.1 µM B2, and 1 µM B2, independently. After 5 days treatment, NaCl was added into the nutrient solution for salt stress. Our results showed that B2 could enhance salt tolerance in maize, especially when the concentration was 1.0 µMol·L−1. Exogenous application of B2 significantly enhanced root growth, and the root/shoot ratio increased by 7.6% after 6 days treatment under salt stress. Compared with control, the ABA level also decreased by 31% after 6 days, which might have resulted in the root development. What is more, B2 maintained higher photosynthetic capacity in maize leaves under salt stress conditions and increased the activity of antioxidant enzymes and decreased the generation rate of reactive oxygen species by 16.48%. On the other hand, B2 can enhance its water absorption ability by increasing the expression of aquaporin genes ZmPIP1-1 and ZmPIP1-5. In conclusion, the novel plant growth regulator B2 can effectively improve the salt tolerance in maize. [ABSTRACT FROM AUTHOR]

Ethephon is plant growth regulator widely used to control maize lodging at the early stage of jointing. However, the function and efficacy of ethephon due to differences of cultivars and maize growing areas remains elusive, necessitating the evaluation of each cultivar's sensitivities prior to the application of ethylene. In this study, we collected ten maize cultivars from the largest planted area in China and cultivated in three typical growing areas to evaluate their sensitivity to ethephon. The results showed that ethephon reduced maize plant height, ear height, length of base internode, and generally increased the crushing strength of maize base internode. These traits may enhance maize lodging resistance by reducing the center of gravity of the plant structure. The effect of ethephon varied across growing areas, and cultivars within the same region exhibited distinct sensitivity levels to ethephon. The crushing strength of the eighth internode in maize exhibits a wide range of change and small coefficient of variation. Hence, this index's change range could be utilized to assess the sensitivity of maize cultivars to ethephon in various regions. In addition to agronomic traits, we detected shifts in transcriptional levels related to the signaling pathways of phytohormones, particularly ethylene and gibberellin. These changes reveal the association between transcriptional signaling levels of key factors and the sensitivity to ethylene in ten maize cultivars. The results contribute to our understanding of the lodging resistance in different maize cultivars and evaluation the sensitivity of maize cultivar to ethephon in different growing areas, with implications for comparable pedo-climatic conditions elsewhere. [Display omitted] • The sensitivity of same cultivar to ETH differed in different growing areas, and within the same growing area. • The sensitivity of different cultivars to ETH can be evaluated by the crushing strength of maize eighth internode. • The sensitivity of different cultivars to ETH correlated to the expression level of ETH receptor. [ABSTRACT FROM AUTHOR]

Maize yield is limited by water deficit in the arid and semiarid regions of China. Conserving water and enhancing crop water productivity are inevitable requirements for the sustainable development of water efficient agriculture. Plant growth regulators (PGRs) play important roles in maize water stress tolerance. In this study, we investigated the effect of plant growth regulator-brazide, a functional analog of brassinolide (BR), on maize water stress resistance through a two-year (2020–2021) field experiment. The experiment included four water treatments (I100: 4012 m3 ha−1; I80: 3210 m3 ha−1; I60: 2407 m3 ha−1; I40: 1605 m3 ha−1), four PGR concentrations (CK: water; Bra: 0.1 μmol L−1 14-hydroxylated brassinosteroid; B1: 0.1 μmol L−1 brazide; B2: 1 μmol L−1 brazide; B3: 10 μmol L−1 brazide). The results showed that deficit irrigation (I60 and I40) decreased soil water content (SWC), photosynthetic rate (Pn), leaf area index (LAI), aboveground biomass (AB) and yield, but improved crop water productivity (WP c). Under deficit irrigation conditions, 1 μmol L−1 brazide application also increased dry matter accumulation and grain yield, a result attributed to improvement of the photosynthetic rate and increases in the root bleeding saps, water productivity. 1 μmol L−1 Brazide application reduced bare tip length, increasing kernel number per ear, thereby increased the yield of I60 and I40 by 15.1% and 11.4% (p ≤ 0.05; 2020), 16.4% and 20.4% (p ≤ 0.001; 2021), respectively. Path analysis showed brazide improved final yields by increasing thousand grain weight (TGW), photosynthetic rate (Pn) and WP c under deficit irrigation. The increase in TGW with brazide treatment was primarily attributed to the increase of Pn. Overall, Brazide increased maize drought resistance mainly by increasing Pn and WP c , with 1 μmol L−1 brazide as an optimal concentration. • A new plant growth regulator, Brazide, was evaluated in maize. • Brazide increased photosynthetic rate and WUE under deficit irrigation. • Application of brazide improved maize growth and grain yield under deficit irrigation. • 1 μmol L−1 brazide as an optimal concentration for maize in arid region of Northwest China. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGRs) play crucial roles in maize drought tolerance. However, most of the studies are focused on seedling stage under greenhouse conditions, little is known on the effects of grain yields at later growth stage under field environment. It is hypothesized that exogenous application of PGRs can increase maize drought tolerance at different growth stages under field conditions. Here we used alginate oligosaccharide (AOS) and coronatine (COR) to investigate the effects of these two PGRs on maize drought tolerance in a two-year field experiment. The results showed that both COR and AOS treatments reduced leaf water loss and significantly increased the relative leaf water content by 12.6% and 13.0%, thus significantly decreasing superoxide anion accumulation by 49% and 42% in maize seedlings. There was no big difference between these two treatments in the seedling stage. In the subsequent reproductive growth period, although both COR and AOS treatments significantly increased leaf photosynthesis and above-ground growth, including photosynthetic rate by 41% and 33%, relative chlorophyll content (SPAD value) by 8.0% and 6.5%, leaf area by 22% and 15%, plant height by 8.3% and 5.9%, dry matter accumulation by 23% and 17%, respectively, under drought conditions, the effect of COR was superior to the AOS, as evidenced by membership function values of COR treatment were 0.12 and 0.08 larger than that of AOS treatment in 2020 and 2021, respectively. Ultimately, COR and AOS treatments significantly increased the grain yields by 21.7% and 16.2% in 2020, 22.3% and 15.7% in 2021, respectively, under drought conditions. Path analysis showed both PGRs increased final grain yields by increasing thousand-kernel weight (TKW). While the TKW increase with COR treatment was mainly due to the increase of relative chlorophyll content (SPAD value), AOS treatment mainly increased dry matter accumulation under drought conditions. [Display omitted] • Effects of coronatine (COR) and alginate oligosaccharide (AOS) on drought tolerance examined. • Both COR and AOS treatments improved maize drought tolerance. • Treatment of maize seedling contributed to the whole growth period. • The COR treatment was more pronounced in the reproductive growth period. • The COR treatment was superior to that of the AOS treatment. [ABSTRACT FROM AUTHOR]