Shiwei Song

Phosphorus Deficiency Restricts Plant Growth but Induces Pigment Formation in the Flower Stalk of Chinese Kale

The effect of phosphorus (P) nutrition on plant growth and pigment formation in the flower stalk was studied under hydroponic conditions for 2 Chinese kale (Brassica alboglabra Bailey) cultivars: ‘Jianyexia’ (green flower stalk) and ‘Hongjiao’ (mauve flower stalk). Three different P treatments were used: 30 (normal-P), 7.5 (low-P), and 0 mg·L−1 (P-deficient). The results showed that the biomass, yield, plant height, stem diameter, and leaf number of Chinese kale were significantly reduced in the low-P and P-deficient treatments compared to the normal-P treatment. The chlorophyll content in the flower stalk epidermis was not affected by different P levels in ‘Jianyexia’, but was significantly reduced by the P-deficient treatment in ‘Hongjiao’. Decreased P levels caused the flavonoid, soluble phenol, and anthocyanin content of the flower stalks to gradually increase in both Chinese kale cultivars. The pH value of the flower stalk epidermis gradually decreased with the declining P levels, and was significantly different among the 3 treatments. As the P levels declined, phenylalanine ammonia-lyase (PAL) and chalcone isomerase (CHI) activities in the flower stalk epidermis gradually increased, and were significantly different among the 3 treatments. P nutrition may control the synthesis of anthocyanins in the flower stalk by regulating the epidermal pH value, and the activities of PAL and CHI.

Dynamics of Nitrogen Speciation in Horticultural Soils in Suburbs of Shanghai, China

Dissolved organic nitrogen (DON) represents a significant pool of soluble nitrogen (N) in soil ecosystems. Soil samples under three different horticultural management practices were collected from the Xiaxiyang Organic Vegetable and Fruit Farm, Shanghai, China, to investigate the dynamics of N speciation during 2 months of aerobic incubation, to compare the effects of different soils on the mineralization of 14C-labeled amino acids and peptides, and to determine which of the pathways in the decomposition and subsequent ammonification and nitrification of organic N represented a significant blockage in soil N supply. The dynamics of N speciation was found to be significantly affected by mineralization and immobilization. DON, total free amino acids, and NH + -N were maintained at very low levels and did not accumulate, whereas NO − -N gradually accumulated in these soils. The conversion of insoluble organic N to low-molecular-weight (LMW) DON represented a main constraint to N supply, while conversions of LMW DON to NH + -N and NH + -N to NO − -N did not. Free amino acids and peptides were rapidly mineralized in the soils by the microbial community and consequently did not accumulate in soil. Turnover rates of the additional amino acids and peptides were soil-dependent and generally followed the order of organic soil > transitional soil > conventional soil. The turnover of high-molecular-weight DON was very slow and represented the major DON loss. Further studies are needed to investigate the pathways and bottlenecks of organic N degradation.

YIELD, FRUIT QUALITY AND NITROGEN UPTAKE OF ORGANICALLY AND CONVENTIONALLY GROWN MUSKMELON WITH DIFFERENT INPUTS OF NITROGEN, PHOSPHORUS, AND POTASSIUM

The effects of varied amounts of fertilization on yield, fruit quality, and nitrogen (N) uptake of muskmelons (Cucumis melo L. var reticulatus Naud) grown under both organic and conventional farming conditions were evaluated. Organic fertilizer (0.0, 0.55, 1.1, and 2.2 kg m−2) and mineral fertilizers containing the same amounts of estimated plant available nutrients [N, phosphorus (P), and potassium (K)] were applied to organic and conventional farming plots, respectively, in both the spring and autumn seasons of 2005. In comparison to conventional farming conditions, muskmelons grown under organic farming conditions had the same yield, total soluble solids (TSS) and soluble sugar contents in both growing seasons, and fruit pulp nitrate content was significantly reduced by 12% on average in spring and 16% on average in autumn. At harvest maturity the aboveground plant N concentration was significantly higher in the conventional treatments than in the organic treatments. At the vine growth stage, the plant N concentrations were similar in all treatments in both seasons. The ratios of nitrate N to total N amount in aboveground biomass were higher in conventional and high fertilized organic treatments than in low or not fertilized organic treatments under limited N supply from the soil. Muskmelon plants absorbed mainly inorganic N, and the protein N fraction in the xylem sap was larger than the amino acid N fraction. Plants grown in the organic system had a higher proportion of organic N in their xylem sap, especially when manure input was low.

Cloning and characterization of the ammonium transporter genes BaAMT1;1 and BaAMT1;3 from Chinese kale

Chinese kale (Brassica alboglabra L.) is a popular vegetable rich in important nutrients. Fertilization with appropriate ammonium:nitrate ratios enhances biomass production and quality. AMT-type ammonium transporters have been shown to mediate ammonium uptake across the plasma membrane. However, very little is known about the molecular regulation of growth and development by ammonium in Chinese kale, including how ammonium regulates the expression of AMT1 genes. In this study, we identified and characterized two AMT1 genes from B. alboglabra, BaAMT1;1 and BaAMT1;3. The full-length open reading frames of BaAMT1;1 and BaAMT1;3 were 1512 bp and 1515 bp, respectively. Transient expression of the fusion proteins pBE-EGFP-BaAMT1;1 and pBE-EGFP-BaAMT1;3 in onion epidermal cells indicated that these transporters are located on the plasma membrane. BaAMT1;1 and BaAMT1;3 were functional in yeast and complemented a mutant defective in ammonium transport. BaAMT1;1 was expressed in vegetative organs and at high levels in roots, while BaAMT1;3 expression was root specific. In addition, we observed opposite responses of BaAMT1;1 and BaAMT1;3 expression to nitrogen starvation and ammonium resupply in roots. These results provide new insights into the molecular mechanisms underlying ammonium absorption in Chinese kale.

Uptake Kinetics of Different Nitrogen Forms by Chinese Kale

ABSTRACT In this paper, the uptake kinetics of various nitrogens (nitrate (NO3−), ammonium (NH4+), urea, amino acid) by Chinese kale (Brassica oleracea L. var. Bailey) were studied under hydroponic condition. The results indicated that the uptake kinetics of organic and inorganic nitrogen (N) by Chinese kale conform to the Michaelis–Menten equation, and the maximum uptake rate (Vmax) and affinity index (1/Km) showed nitrate (NO3—N) > ammonium (NH4+-N) > urea-N > Gly-N, with significant differences between treatments (p < 0.05). Adding different types of N to NO3− nutrient solution had little impact on its affinity, but significantly decreased the NO3− Vmax, which showed NO3–N > NO3− + NH4+ > NO3− + urea > NO3− + Gly. Chinese kale preferred inorganic N to organic N, with NO3− preceding NH4+. Adding organic and NH4+ N to nutrient solution reduced the NO3− uptake capacity by the plant.

Effect of Ammonium and Nitrate Ratios on Growth and Yield of Flowering Chinese Cabbage

The effect of different ammonium and nitrate ratios (NH4 + -N : NO3 −-N = 0:100, 25:75, 50:50 and 75:25) on growth and yield of flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) with 3 cultivars were studied in hydroponics. The results indicated that, compared with the complete nitrate treatment, plant height, stem diameter and biomass of flowering Chinese cabbage were increased in the low enhancement of ammonium (25%) in nutrient solution, while plant growth and biomass were decreased in the medium (50%) and high (75%) enhancement of ammonium. Compared with the complete nitrate treatment, low enhancement of ammonium (25%) in nutrient solution increased root activity of flowering Chinese cabbage, while it was decreased by the medium (50%) and high (75%) enhancement of ammonium treatments. Nutrient solution with 25% ammonium enhancement maintained a high root absorption capacity and increased plant biomass, so it was appropriate to hydroponics for flowering Chinese cabbage.

Genome-wide identification, phylogenetic analysis, and expression profiling of polyamine synthesis gene family members in tomato

Polyamines (PAs), including putrescine (Put), spermidine (Spd), spermine (Spm), and thermospermine (T-Spm), play key roles in plant development, including fruit setting and ripening, morphogenesis, and abiotic/biotic stress. Their functions appear to be intimately related to their synthesis, which occurs via arginine/ornithine decarboxylase (ADC/ODC), Spd synthase (SPDS), Spm synthase (SPMS), and Acaulis5 (ACL5), respectively. Unfortunately, the expression and function of these PA synthesis-relate genes during specific developmental process or under stress have not been fully elucidated. Here, we present the results of a genome-wide analysis of the PA synthesis genes (ADC, ODC, SPDS, SPMS, ACL5) in the tomato (Solanum lycopersicum). In total, 14 PA synthesis-related genes were identified. Further analysis of their structures, conserved domains, phylogenetic trees, predicted subcellular localization, and promoter cis-regulatory elements were analyzed. Furthermore, we also performed experiments to evaluate their tissue expression patterns and under hormone and various stress treatments. To our knowledge, this is the first study to elucidate the mechanisms underlying PA function in this variety of tomato. Taken together, these data provide valuable information for future functional characterization of specific genes in the PA synthesis pathway in this and other plant species. Although additional research is required, the insight gained by this and similar studies can be used to improve our understanding of PA metabolism ultimately leading to more effective and consistent plant cultivation.

Influence of inorganic and organic nitrogen on enzymes of nitrogen assimilation and growth in tomato seedlings

Summary Recent evidence suggests that agricultural and horticultural crops may be able to take up significant quantities of dissolved organic nitrogen (DON). Our aims were to determine the effects of supplying different forms of N on growth and on the activities of N-assimilatory enzymes in tomato. Two genotypes of tomato were grown in sterile hydroponic culture without N (control), with NO3– or NH4+ (3 mM), or with organic-N in the form of glycine (1.5, 3.0, or 6.0 mM). The results showed that biomass production and N-contents were similar in both genotypes when supplied with NO3– or with glycine, and that this growth was much greater than in plants supplied with NH4+ alone, or without added N. In addition, the production of plant biomass was positively correlated with the concentration of glycine-N used; however, the magnitude of the response was genotype-dependent. The form of N supplied also significantly affected the activities of several key N-assimilatory enzymes in roots and shoots. For example, addition of glycine increased the activities of NADH-glutamate dehydrogenase (NADH-GDH), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) in roots, compared with the NO3– or NH4+ treatments. Our results clearly demonstrate the intrinsic ability of tomato plants to use DON as a sole source of N. Further studies to investigate the functional significance of DON in horticultural systems under non-sterile conditions are therefore warranted.

Genome-wide identification, phylogeny analysis, expression profiling, and determination of protein-protein interactions of the LEUNIG gene family members in tomato

Members of the LEUNIG gene family have recently emerged as key players in gene repression, affecting several developmental mechanisms in plants, especially flower development. LEUNIG proteins function via recruiting adaptor SEUSS proteins. Nevertheless, no systematic studies on the LEUNIG and SEUSS gene families have been undertaken in tomato (Solanum lycopersicum, a fleshy fruit-bearing model plant, belonging to the Solanaceae family). Here, we present the results of a genome-wide analysis of tomato LEUNIG and SEUSS genes. In our study, we identified three SlLUG and four SlSEU genes. All three SlLUG full-length proteins contained the LEUNIG canonical domains (LUFS and two WD40 repeats), and the four full-length SlSEU genes contained the Lim-binding domain. All the members of the SlLUG and SlSEU family proteins were localized to the nucleus. All the SlSEU and SlLUG genes were detected in the tomato tissues tested. Expression analysis showed that the SlLUGs and SlSEUs exhibited tissue-specific expression, and that they responded to exogenous plant hormone and stress treatment. Protein-protein interaction analysis showed that only SlLUGs, but not SlSEUs, interacted with SlYABBY. Only a weak interaction between SlLUG1 and SlSEU3 was observed among all the SlLUG and SlSEU proteins. Taken together, these findings may help elucidate the roles played by SlLUG and SlSEU family members in plant growth and development.

Effects of partial replacement of nitrate with different nitrogen forms on the yield, quality and nitrate content of Chinese kale

ABSTRACT In this study, the yields, nutritional qualities and nitrate (NO3) content of Chinese kale were studied with two cultivars, following partial replacement of nitrate (20%) with ammonium (NH4), urea and glycine in hydroponics. The results showed that, compared with the full nitrate treatment, ammonium replacement increased the fresh weight by 18.1% and 8.0% of ‘Zaobao’ and ‘Lvbao’ cultivars respectively, whereas urea and glycine replacements decreased the biomass significantly. Adding different nitrogen (N) forms significantly improved the contents of vitamin C, soluble sugar, free amino acid, protein, soluble phenol and flavonoids in Chinese kale. Adding the three alternative N forms also reduced nitrate content significantly, in which glycine replacement was the lowest. According to the results obtained, different forms of N replacement could be used for different purposes. Glycine replacement could be the best alternative only to improve qualities, while ammonium replacement could be the best alternative to improve both the yield and qualities.