Growth regulating factors (GRFs) have been shown to play important roles in plant growth and development. GRF genes represent a large multigene family in plants. Recently, genome-wide structural and evolutionary analyses of the GRF gene families in Arabidopsis, rice, and maize have been reported. Chinese cabbage (Brassica rapa L. ssp. pekinensis) is one of the most important vegetables for agricultural production, and a full genome assembly for this plant has recently been released. However, to our knowledge, the GRF gene family from Chinese cabbage has not been characterized in detail. In this study, genome-wide analysis was carried out to identify all the GRF genes in Chinese cabbage. Based on the complete Chinese cabbage genome sequence, 17 nonredundant GRF genes, named BrGRFs, were identified and classified into six groups. Phylogenetic analysis of the translated GRF protein sequences from Chinese cabbage, Arabidopsis, and rice indicated that the Chinese cabbage GRF proteins were more closely related to the GRF proteins of Arabidopsis than to those of rice. Expression profile analysis showed that the BrGRF genes had uneven transcript levels in different organs or tissues, and the transcription of most BrGRF genes was induced by gibberellic acid (GA3) treatment. Additionally, over-expression of BrGRF8 in transgenic Arabidopsis plants increased the sizes of the leaves and other organs by regulation of cell proliferation. The data obtained from this investigation will contribute to a better understanding of the characteristics of the GRF gene family in Chinese cabbage, and provide a basis for further studies to investigate GRF protein function during development as well as for Chinese cabbage-breeding programs to improve yield and/or head size.

Current colorimetric methods for quantitative determination of seed viability (SV) with 2,3,5-triphenyl tetrazolium chloride (TTC) have been plagued by issues of being cumbersome and time-consuming during the experimental process, slow in extraction and staining, and exhibiting inconsistent results. In this work, we introduced a new approach that combines TTC-staining with high-temperature extraction using dimethyl sulfoxide (DMSO). The optimization of the germination stage, TTC-staining method, and 1,3,5-triphenylformazan (TTF) extraction method were meticulously carried out as follows: When the majority of wheat seeds had grown the radicle, and the length of radicles was approximately equal to the seed length (24 h-germination), 2 g germinating seeds were placed into a beaker (20 mL) containing 5 mL 10 g·L⁻¹ TTC solution. The seeds were stained with TTC in the dark at 25 °C for 1 h. Following the staining, 1 mL 1 mol·L⁻¹ H₂SO₄ was added to stop the reaction for 5 min. The H₂SO₄ solution was then removed, and the seeds were gently rinsed with deionized water. Subsequently, the TTF produced in the seeds was extracted directly with 5 mL DMSO solution at 55 °C for 1 h. The absorbance of the extract was measured at 483 nm, and the index of SV was calculated according to a predetermined TTC calibration curve and expressed by mg TTC·g⁻¹ (seed)·h⁻¹. The new method has been demonstrated to be rapid, stable, and highly sensitive, as evidenced by the accurate measurement of seed viability with different aging degrees.

Salt stress is one of the major abiotic stresses that severely impact plant growth and development. In this study, we investigated the physiological and transcriptomic responses of Chinese cabbage “Qingmaye” to salt stress, a main variety in North China. Our results showed that the growth and photosynthesis of Chinese cabbage were significantly inhibited by salt treatment. However, as a glycophyte, Chinese cabbage could cope with high salinity; it could complete an entire life cycle at 100 mM NaCl. The high salt tolerance of Chinese cabbage was achieved by accumulating osmoprotectants and by maintaining higher activity of antioxidant enzymes. Transcriptomic responses were analyzed using the digital gene expression profiling (DGE) technique after 12 h of treatment by 200 mM NaCl. A total of 1235 differentially expressed genes (DEGs) including 740 up- and 495 down-regulated genes were identified. Functional annotation analyses showed that the DEGs were related to signal transduction, osmolyte synthesis, transcription factors, and antioxidant proteins. Taken together, this study contributes to our understanding of the mechanism of salt tolerance in Chinese cabbage and provides valuable information for further improvement of salt tolerance in Chinese cabbage breeding programs.

The biological effects of strontium (88Sr) on Chinese cabbage | Weirong Zhang, Zheng Kang, Qiang Wang, Nianwei Qiu, Min Chen, Feng Zhou | Agricultural Journals

Low concentration strontium (LC-Sr) can promote the growth of plants. In order to explore its promoting mechanism from the aspect of photosynthesis, the leaf characteristics, CO₂ assimilation and chlorophyll (Chl) a fluorescence kinetics were investigated with hydroponically LC-Sr-treated Chinese cabbage seedlings. After a 28-d treatment to SrCl₂ at different concentrations (0.1, 0.2, 0.5, and 1.0 mmol L^-1), we observed an increase in the specific leaf weight (SLW) of Chinese cabbage compared with the control group. Notably, as the strontium concentration increased, a more pronounced improvement trend in the contents of Chl and protein in the leaves was observed, contributing to the enhancement of photosynthesis. However, the statistical differences in P_n among various LC-Sr treatments were not significant. Nevertheless, the leaf starch content exhibited a significant increase after LC-Sr treatments. Additionally, Chl a fluorescence transient has been used as a sensitive indicator of the promotional effect of LC-Sr on photosynthesis. The results of fluorescence parameters showed that LC-Sr treatments accelerated the light reaction speed of leaves (T_fm, dV/dt_o, dVG/dt_o), improved the energy utilization efficiency of photosystem (PSI and PSII) (ETo/CSo, ψ_ET,ψ_RE, δ_Ro, φ_Ro), and ultimately enhanced the photosynthetic performance of leaves (PI_abs, SFI_abs, DF_abs). The increased RCs/CSo and Sm contributed to the enhancement of the light reaction activity of strontium-treated leaves. The LC-Sr treatments had no interference with the calcium absorption, and notably enhanced the photosynthetic capacity of Chinese cabbage, shedding light on potential benefits of LC-Sr for crop cultivation.