Plant hormones (Literature sources on phytohormones and plant signalling)

Science of The Total Environment (2023)

Highlights • R. qingshengii plus N fertilizers boost HM accumulation in Brassica juncea L. • Nitrate is more effective in phytoextraction with R. qingshengii than urea/ammonium • N fertilizers enhance phytoremediation by ABA-catabolizing bacteria 

Abstract: "Bacterial-assisted phytoextraction is an attractive strategy to enhance the phytoremediation efficiency of heavy metal (HM)-contaminated soils. In the present study, we investigated the synergistic effects of N fertilizers and abscisic acid (ABA)-catabolizing bacteria on the HM (Cd, Zn, and Pb) phytoremediation efficiency of Brassica juncea L. (B. juncea). Compared with Rhodococcus qingshengii (R. qingshengii) alone, urea, ammonium‑nitrogen (NH4+-N), and nitrate‑nitrogen (NO3−-N) fertilizers combined with R. qingshengii increased HM concentrations in B. juncea by 13.8 %–48.2 %, 44.2 %–54.4 %, and 59.4 %–113.6 %, respectively, and enhanced the biomass of B. juncea by 7.7 %–38.8 %, 10.9 %–29.5 %, and 19.9 %–46.8 %, respectively. Consequently, the bioconcentration factor increased by 3.4 %–30.9 % and the phytoextraction rate increased by 18.5 %–98.7 %. Treatment with NO3−-N showed the most significant effect. In structural equation modeling, R. qingshengii inoculation showed greater path coefficients with soil pH and ABA and indoleacetic acid concentrations of B. juncea than N fertilization, indicating that R. qingshengii contributed more to HM extraction efficiency than N fertilizers. Additionally, differences in the extraction rates of Cd, Zn, and Pb from B. juncea were reduced following N fertilization. In summary, synergistic R. qingshengii inoculation and N fertilization have substantial potential to enhance phytoremediation efficiency. Combined application of R. qingshengii and NO3−-N fertilizers is recommended."

Plant Communications (2022)

Abstract: "Nitrate (NO3-) is not only an essential nutrient but also an important signal molecule for plant growth. Low nitrogen use efficiency (NUE) of crops causes increasingly serious environmental and ecological problems. Understanding the molecular mechanisms of NO3- regulation in crops is crucial for NUE improvement in agriculture. During last several years, significant progress has been made on the regulation of NO3- signaling in crops and some key factors of NO3- signaling have been characterized to play important roles in NO3- utilization. However, no detailed reviews have been reported from this view. Here, we mainly focused on the recent advances of NO3- signaling in crops including the short-term signaling, the long-term signaling and the impact of environmental factors. We also reviewed the regulation of the crucial genes involved in NO3- signaling on NUE of crops. This review will provide useful information for further research on NO3- signaling in crops and a theoretical basis for breeding new crop varieties with high NUE, which is of great significance for sustainable agriculture."

Industrial Crops and Products (2023)

Highlights: • Calcium nitrate treatment induced calcium and nitrate signal transductions. • Through nitrate and calcium signal transductions, gibberellin biosynthesis and signal transduction were promoted. • Gibberellin signal transformation induced the expression of downstream genes to further change the cell structures. • This study proposed a pathway through which calcium nitrate promoted the stem elongation of Dendrobium officinale. 

Abstract: "Dendrobium officinale Kimura et Migo is a precious medicinal plant which has high medicinal and commercial value. The length of the stem of D. officinale is an important factor affecting the yield because of its bioactive polysaccharides found in the stem. Nitrate can promote the elongation of young stems, but the mechanisms of calcium nitrate (CN) mediated stem length growth remain largely unknown. In this study, the transcriptome, main organic components, mineral elements and microstructure of D. officinale sprayed with CN were analyzed. 659 differentially expressed genes (DEGs) were detected in the Control and CN treatment. The concentrations of the calcium and nitrate increased significantly, while the concentrations of two kinds of the aldohexoses decreased significantly. Most of the twenty key genes involved in calcium and nitrate signal transduction and carbohydrate metabolism were up-regulated. In the two pathways of gibberellin (GA) biosynthesis and signal transduction, it was found that the expression of four differential genes related to GA biosynthesis was up-regulated, and the contents of nine GAs were also significantly increased, especially the contents of bioactive GA1 and GA4. The expression levels of most genes related to GA signal transduction were also up-regulated after CN treatment. After CN treatment, the expression levels of downstream genes related to stem elongation and tillering were also up-regulated. In addition, the microstructure showed that CN treatment made cells elongate longitudinally, made cell walls and collenchyma thicken, made obvious lignification and the increased the number of vascular bundles, indicating that CN can promote stem elongation by enhancing ductility and mechanical strength. These results provide a theoretical and practical basis for studying how nitrate treatment can improve the stem length and yield of D. officinale."