Abscisic acid (ABA), as a commonly used plant growth regulator, is easy to be degraded and lose its bioactivity under sunshine. To select an eco-friendly and efficient photoprotectant for the improvement of photostability and bioactivity of ABA when exposed to ultraviolet (UV) light, we tested the effects of three biodegradable natural-derived high polymers, sodium lignosulfonates 3A [molecular weight (MW) > 50000, with degree of sulfonation (DS) of 0.48] and NA (20000 < MW < 50000, with DS of 0.7) and calcium lignosulfonate CASA (MW < 20000, with DS of 0.7), on the photodegradation of ABA. Lignosulfonates 3A, NA, and CASA showed significant photostabilizing capability on ABA. Lignosulfonate 3A showed preferable photostabilizing effects on ABA compared to CASA, while NA showed an intermediate effect. That indicated that lignosulfonate with a high MW and low DS had a stronger UV absorption and the hollow aggregate micelles formatted by lignosulfonate protect ABA from UV damage. Approximately 50% more ABA was kept when 280 mg/L ABA aqueous solution was irradiated by UV light for 2 h in the presence of 2000 mg/L lignosulfonate 3A. The bioactivity on wheat (JIMAI 22) seed germination was greatly kept by 3A in comparison to that of ABA alone. The 300 times diluent of 280 mg/L ABA plus 2000 mg/L 3A after 2 h of irradiation showed 20.8, 19.3, and 9.3% more inhibition on shoot growth, root growth, and root numbers of wheat seed, separately, in comparison to ABA diluent alone. We conclude that lignosulfonate 3A was an eco-friendly and efficient agent to keep ABA activity under UV radiation. This research could be used in UV-sensitive and water-soluble agrichemicals and to optimize the application times and dosages of ABA products.

Background Lodging is one of the important factors causing maize yield. Plant height is an important factor in determining plant architecture in maize (Zea mays L.), which is closely related to lodging resistance under high planting density. Coronatine (COR), which is a phytotoxin and produced by the pathogen Pseudomonas syringae, is a functional and structural analogue of jasmonic acid (JA). Results In this study, we found COR, as a new plant growth regulator, could effectively reduce plant height and ear height of both hybrids (ZD958 and XY335) and inbred (B73) maize by inhibiting internode growth during elongation, thus improve maize lodging resistance. To study gene expression changes in internode after COR treatment, we collected spatio-temporal transcriptome of inbred B73 internode under normal condition and COR treatment, including the three different regions of internode (fixed, meristem and elongation regions) at three different developmental stages. The gene expression levels of the three regions at normal condition were described and then compared with that upon COR treatment. In total, 8605 COR-responsive genes (COR-RGs) were found, consist of 802 genes specifically expressed in internode. For these COR-RGs, 614, 870, 2123 of which showed expression changes in only fixed, meristem and elongation region, respectively. Both the number and function were significantly changed for COR-RGs identified in different regions, indicating genes with different functions were regulated at the three regions. Besides, we found more than 80% genes of gibberellin and jasmonic acid were changed under COR treatment. Conclusions These data provide a gene expression profiling in different regions of internode development and molecular mechanism of COR affecting internode elongation. A putative schematic of the internode response to COR treatment is proposed which shows the basic process of COR affecting internode elongation. This research provides a useful resource for studying maize internode development and improves our understanding of the COR regulation mechanism based on plant height.

Core Ideas This study examined a new way to mitigate the effects of HTS on spring maize. B2 had similar effects to ABA on alleviating maize yield penalty caused by HTS. B2 reduced plant height and ear height. Adopting spring maize (Zea mays L.) to replace part of a winter wheat (Triticum aestivum L.)–summer maize rotation system can mitigate agricultural water scarcity in the North China Plain. The main obstacle to increasing spring maize production is high‐temperature stress (HTS) at grain‐filling stage. In this study, a novel plant growth regulator (2,4‐dichloroformamide cyclopropane acid [B2]), based on the structures of abscisic acid (ABA), pyrabactin, and coronatine, was used to reduce maize yield penalty imposed by HTS. Field experiments were conducted to investigate the effects of B2 on alleviating maize yield penalty caused by HTS in 2015 and 2016. The hybrid maize cultivar Zhengdan958, which is widely planted across China, was grown at a density of 67,500 plants ha−1. Water, B2, and ABA were applied to maize foliar surfaces at the ninth‐expanded‐leaf stage. Application of B2 significantly increased grain yield by 8.5% by increasing thousand‐kernel weight and decreasing bare tip length compared with the control. Additionally, B2 significantly increased the SPAD value and ABA content of the ear leaf, enhancing net photosynthesis rate and heat resistance. Application of B2 also improved grain‐filling rate, grain volume, and grain dry weight, which contributed to higher grain yield. Moreover, B2 decreased plant and ear height, neither of which was affected by ABA. These results indicate that B2, with a biological activity similar that of ABA, could help maintain relatively higher photosynthetic capacity, heat resistance, and grain‐filling rate during the grain‐filling stage under HTS, providing a stable method to increase grain yield.

Lodging is a threat for maize production worldwide. Coronatine (COR) is a jasmonic acid analog hopeful to be a new plant growth regulator in agriculture. In this study, we demonstrated that the plant height of ZD958 and XY335, two cultivated maize hybrids, was significantly decreased under COR treatment via reducing internode length and thus improve lodging resistance. To explore gene expression changes driving the responses of internode to COR, spatio-temporal transcriptomic data of inbred