Effects of Root Temperature on the Plant Growth and Food Quality of Chinese Broccoli (Brassica oleracea var. alboglabra Bailey)

Optimized Design of Irrigation Water-Heating System and Its Effect on Lettuce Cultivation in a Chinese Solar Greenhouse

In cold regions, the low irrigation water temperature is an important factor of low-temperature stress for greenhouse crops. In this paper, an irrigation water-heating system (IWHS) is proposed to increase the water temperature by utilizing the excess heat in the solar greenhouse. The heat-collection capacity of the system was analyzed by screening the IWHS process parameters in a Chinese solar greenhouse, and a warm-water irrigation experiment for lettuce was conducted. The results demonstrated that the water temperature increased with the increase in wind speed, and the increase in daily average water temperature reached the maximum value of 8.6 °C at 4.5 m/s wind speed. When the heat exchanger was installed at a height of 3.0 m, the collector capacity increased by 17.8% and 6.0% compared with the heating capacity at 0 m and 1.5 m, respectively, and the operation termination water temperature was 22.0-32.2 °C and its coefficient of performance (COP) was optimal. Surface darkening of the heat exchanger did not affect the heat-collection capacity of the system. Using the IWHS effectively improved the temperature of lettuce irrigation water in the Chinese solar greenhouse. The increased frequency of warm-water irrigation significantly promoted lettuce growth and increased the average yield per plant by 15.9%. Therefore, IWHS effectively increased the irrigation water temperature in a Chinese solar greenhouse in winter. Improving the system would enhance its economic and application value.

Assessing the efficacy of phyllospheric growth-promoting and antagonistic bacteria for management of black rot disease of cauliflower incited by Xanthomonas campestris pv. campestris

The study aimed to assess the potential of phyllospheric bacterial strains isolated from cauliflower plants as biocontrol agents against black rot disease caused by Xanthomonas campestris pv. campestris, through both in vitro and in vivo evaluations. A total of 46 bacterial strains were isolated from healthy and infected cauliflower leaves of both resistant and susceptible plants, and evaluated them for various traits, including plant growth-promoting activities and in vitro antagonistic activity against Xanthomonas campestris pv. campestris. Further, a pot experiment was conducted with the susceptible cauliflower genotype (Pusa Sharad) and 10 selected phyllospheric bacterial isolates to assess their biocontrol efficacy against the disease. The results showed that 82.60% of phyllospheric bacterial isolates were positive for phosphate solubilization, 63.04% for ammonia production, 58.69% for HCN production, 36.95% for siderophore production, and 78.26% had the capacity to produce IAA. Out of the 46 isolates, 23 exhibited in vitro antagonistic activity against X. campestris pv. campestris and 10 isolates were selected for a pot experiment under glasshouse conditions based on their good plant growth-promoting activities and antagonistic assay. The results revealed that bacterial isolate CFLB-27 exhibited the highest biocontrol efficiency (65.41%), followed by CFLB-24 (58.30%), CFLB-31 (47.11%), and CFLB-26 (46.03%). These four isolates were identified as Pseudomonas fluorescens CFLB-27, Bacillus velezensis CFLB-24, Bacillus amyloliquefaciens CFLB-31, and Stenotrophomonas rhizophila CFLB-26. This study provides valuable insights into the potential of phyllospheric bacteria as an effective tool for disease management in sustainable agriculture.

A short-term cooling of root-zone temperature increases bioactive compounds in baby leaf Amaranthus tricolor L

Leafy vegetables that are offered as seedling leaves with petioles are referred to as baby leaf vegetables. One of the most nutritious baby leaves, amaranth (Amaranthus tricolor L.), contains several bioactive compounds and nutrients. Here, we investigated the growth and quality of baby leaf amaranth using a variety of short-term cooling root-zone temperatures (RZT; 5, 10, 15, and 20°C), periods (1, 3, 5, and 7 days), and combinations thereof. We observed that exposing amaranth seedlings to RZT treatments at 5 and 10°C for 1-3 days increased the antioxidant capacity and the concentrations of bioactive compounds, such as betalain, anthocyanin, phenolic, flavonoid, and ascorbic acid; however, extending the treatment period to 7 days decreased them and adversely affected growth. For RZT treatments at 20°C, leaf photosynthetic pigments, bioactive compounds, nutrients, and antioxidant capacity increased gradually as the treatment period was extended to 7 days. The integration of RZTs at 5 and 10°C for one day preceded or followed by an RZT treatment at 20°C for 2 days had varied effects on the growth and quality of amaranth leaves. After one day of RZT treatment at 5°C followed by 2 days of RZT treatment at 20°C, the highest concentrations of bioactive compounds, nutrients, and antioxidant capacity were 1.4-3.0, 1.7, and 1.7 times higher, respectively, than those of the control, and growth was not impaired. The short-term cooling RZT treatments under controlled environments were demonstrated to be adequate conditions for the improvement of target bioactive compounds in amaranth baby leaf without causing leaf abnormality or growth impairment.

Purple stem Brassica napus exhibits higher photosynthetic efficiency, antioxidant potential and anthocyanin biosynthesis related genes expression against drought stress

Purple-stem Brassica napus (B. napus) is a phenotype with unique color because of its high anthocyanins content. Anthocyanins are naturally occurring plant pigments that have antioxidants activity and play important role in plant defense against abiotic and biotic stresses. In the present study, drought induced effects on plants were investigated in hydroponically grown seedlings of green stem (GS) and purple stem (PS) genotypes of B. napus. The results of this study showed that the major function of anthocyanins accumulation during drought was to enhance the antioxidant capability and stress tolerance in B. napus plants. Our results showed that drought significantly inhibited the plant growth in terms of decreased biomass accumulation in both genotypes, although marked decline was observed in GS genotype. The reduction in photosynthetic attributes was more noticeable in the GS genotype, whereas the PS genotype showed better performance under drought stress. Under stressful conditions, both the genotype showed excessive accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as higher levels of antioxidant enzymes activities. Under drought conditions, the GS genotype showed apparent damages on chloroplast deformation like in thylakoid membrane and grana structural distortion and fewer starch grains and bigger plastoglobuli. Moreover, during drought stress, the PS genotype exhibited maximum expression levels of anthocyanins biosynthesis genes and antioxidant enzymes accompanied by higher stress tolerance relative to GS genotype. Based on these findings, it can be concluded that GS genotype found more sensitive to drought stress than the PS genotype. Furthermore this research paper also provides practical guidance for plant biologists who are developing stress-tolerant crops by using anthocyanin biosynthesis or regulatory genes.

Tissue-specific distribution of primary and secondary metabolites of Baemoochae (×Brassicoraphanus) and its changes as a function of developmental stages

The distribution and changes in the primary and secondary metabolite profiles of Baemoochae, an inter-generic hybrid of Chinese cabbage and radish, during the plant's developmental stages were investigated. Metabolites were analyzed using gas chromatography-mass spectrometry (GC-MS) and ultra-high-performance liquid chromatography-electrospray ionization-quadrupole time-of-flight (UHPLC-ESI-qTOF MS). Free sugar, organic acid, and amino acid composition depended on the tissue type and developmental stage of Baemoochae. For example, glucose and alanine levels were higher in mature leaves than in young leaves; citric acid content in mature roots was lower than that in young roots. Several glucosinolates were identified for the first time in Baemoochae. Glucoraphasatin was predominant in both leaves and roots, regardless of plant maturity. Total glucosinolate content was significantly higher in roots than in leaves and in mature than in young plants. The roots of mature Baemoochae could be used as a rich source of glucosinolates, with several potential health-promoting effects.

Method validation and residue analysis of methoxyfenozide and metaflumizone in Chinese broccoli under field conditions by liquid chromatography with tandem mass spectrometry

Methoxyfenozide and metaflumizone are insecticides used on Chinese broccoli to prevent insects and increase yield. However, the residues are potentially harmful to the environment and consumers. In this study, the quick, easy, cheap, effective, rugged, safe method with high-performance liquid chromatography with tandem mass spectrometry was modified and validated for determination of methoxyfenozide and metaflumizone in Chinese broccoli. The clean-up efficiency of different sorbents including C₁₈ , primary secondary amine, graphitized carbon black, and carbon nanofiber was compared. Recoveries of the validated method were 71.8-94.6% with relative standard deviations of 1.5-3.2% and the limits of quantification were 0.01 and 0.005 mg/kg for methoxyfenozide and metaflumizone, respectively. A storage stability test showed almost no degradation of methoxyfenozide in Chinese broccoli, however, the degradation rate of metaflumizone was 22.9% after 10-wk storage at -20°C. In field trials in four producing regions, the dissipation of both methoxyfenozide and metaflumizone in Chinese broccoli was fast, with half-lives of only 1.0-5.1 and 0.7-2.5 days, respectively. Terminal residues after application of the two pesticides were all below 1.0 mg/kg after 5 days.

Drought tolerance in Brassica napus is accompanied with enhanced antioxidative protection, photosynthetic and hormonal regulation at seedling stage

Climate change, food insecurity, water scarcity, and population growth are some of today's world's frightening problems. Drought stress exerts a constant threat to field crops and is often seen as a major constraint on global agricultural productivity; its intensity and frequency are expected to increase in the near future. The present study investigated the effects of drought stress (15% w/v polyethylene glycol PEG-6000) on physiological and biochemical changes in five Brassica napus cultivars (ZD630, ZD622, ZD619, GY605, and ZS11). For drought stress induction, 3-week-old rapeseed oil seedlings were treated with PEG-6000 in full strength Hoagland nutrient solution for 7 days. PEG treatment significantly decreased the plant growth and photosynthetic efficiency, including primary photochemistry (Fv/Fm) of PSII, intercellular CO₂ , net photosynthesis, chlorophyll contents, and water-use efficiency of all studied B. napus cultivars; however, pronounced growth retardations were observed in cultivar GY605. Drought-stressed B. napus cultivars also experienced a sharp rise in H₂ O₂ generation and malondialdehyde (MDA) content. Additionally, the accumulation of ROS was accompanied by increased activity of enzymatic antioxidants (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase), although the increase was more obvious in ZD622 and ZS11. Drought stress also caused an increased endogenous hormonal biosynthesis (abscisic acid, jasmonic acid, salicylic acid) and accumulation of total soluble proteins and proline content, but the extent varies in B. napus cultivars. These results suggest that B. napus cultivars have an efficient drought stress tolerance mechanism, as shown by improved antioxidant enzyme activities, photosynthetic and hormonal regulation.

Plant biology for space exploration - Building on the past, preparing for the future

A review of past insights of space experiments with plants outlines basic space and gravity effects as well as gene expression. Efforts to grow plants in space gradually incorporated basic question on plant productivity, stress response and cultivation. The prospect of extended space missions as well as colonization of the Moon and Mars require better understanding and therefore research efforts on biomass productivity, substrate and water relations, atmospheric composition, pressure and temperature and substrate and volume (growth space) requirements. The essential combination of using plants not only for food production but also for regeneration of waste, and recycling of carbon and oxygen production requires integration of complex biological and engineering aspects. We combine a historical account of plant space research with considerations for future research on plant cultivation, selection, and productivity based on space-related environmental conditions.