Search

The effects of plant hormones on plant growth of Zizania latifolia are still considered to be the difficult and hot spots. The present study was carried out to investigate the regulation mechanism of exogenous indole-3-acetic acid (IAA) and IAA transport inhibitor (2,3,5-triiodobenzoic acid, TIBA) on yield, photosynthesis capacity, carbon assimilation and interaction of plant-fugal of Ustilago esculenta Henn. These results displayed that exogenous IAA led to significant increases in gall growth rate, swollen gall volume and biomass accumulation, promoting yield per unit of swollen gall in Z. latifolia. Exogenous IAA could improve the net photosynthetic rate (Pn), which contributed to higher stomatal conductance (Gs) and transpiration rate (Tr) in plant. TIBA treatment markedly inhibited the plant growth and photosynthetic rate. Contents of sucrose, glucose, fructose and total soluble sugar by IAA were significantly higher than control, whereas these parameters were declined by TIBA. Exogenous TIBA resulted in accumulation of starch (unfavorable to sugar metabolism) and crude fiber contents (declined swollen gall quality). Additionally, it was firstly reported the stimulation of exogenously applied of IAA and TIBA on plant growth and hyphae growth of U. esculenta. Microscopic analyses revealed that abundant hyphae were well-distributed closely to cell wall after IAA treatment, which could produce endogenous plant hormones, promoting the swollen cell structure enlargement. And hyphal aggregation over-growth by TIBA treatment indicated the vigorously increase of hyphae was surpassed the plant self-growth. These changes were greatly contributed to the increase of endogenous IAA content. The utilization of exogenous IAA and TIBA in present study proved IAA played a dominant role in regulating Z. latifolia growth.

High temperature stress (>30 °C) from late summer to early fall is one of the main limiting factors in wucai ( Brassica campestris L.) growth in southern China. To assess the osmotic and antioxidative reponses of two wucai genotypes (WS-6 and WS-1) differing in heat tolerance, three-week-old seedlings were subjected to three heat-stress treatments for 5 days. Heat treatments above at 30 °C resulted in significant decreases in leaf area and leaf relative water content (RWC) in both genotypes, but being more in heat-sensitive WS-6. This was due to greater accumulations of osmolytes including soluble sugar, soluble protein and proline (Pro), as well as higher levels of reduced ascorbic acid (AsA) and glutathione (GSH) in heat-tolerant WS-1 under heat stress as compared to those in heat-sensitive WS-6. It is worthy noting that mild hyperthermia (30 °C) caused significant increases of AsA and GSH in both genotypes, which might be resulted from their enhanced activities of monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), helping recycle AsA and GSH. In contrast, the AsA and GSH levels of both genotypes were decreased markedly at 40 °C, especially in heat-sensitive WS-6, despite that the enzymes (DHAR and GR) activities involved in their regeneration remained high levels as compared to their respective controls. In addition, larger decrease in total antioxidant capacity (T-AOC) by heat stress was observed in WS-6 than in WS-1. Our results indicated that the heat-sensitive and the heat-tolerant genotype of wucai might possess the same pathway but different capacities of antioxidant defences to cope with heat stress.

Ogura cytoplasmic male sterility (ogu-CMS) has been widely used by breeders for vegetables in the genus Brassica; however, the molecular mechanism of this male sterility remains unclear. The tapetum plays a crucial role in anther development by providing nutrients and secreting callose for pollen development. In this study, we found that the tapetum was abnormally vacuolated after meiosis in Wucai ogu-CMS, which led to the abortion of microspores. The TDF1 gene is essential for early tapetal development. Combined with the characteristics of abortion in ogu-CMS, qRT-PCR analysis showed that the BrTDF1 gene was expressed in all detected tissues from fertile plants, and the transcript levels of this gene in fertile buds were far higher than those in vegetative organs. Compared with the fertile line, BrTDF1 exhibited lower expression in all developmental stages of buds from the sterile line. In addition, the examinations of A6 and EXPB5 genes suggested that the expressions of these genes in ogu-CMS were lower than those in its maintainer line. Further analysis of its function showed that constitutive expression of BrTDF1 in the Arabidopsis tdf1 mutant transgenic lines could restore its fertility. These results indicated that this MYB transcription factor BrTDF1 is required for tapetal development in Wucai.