Dissolved biochar fractions and solid biochar particles inhibit soil acidification induced by nitrification through different mechanisms.

Biochar can inhibit soil acidification by decreasing the H+ input from nitrification and improving soil pH buffering capacity (pHBC). However, biochar is a complex material and the roles of its different components in inhibiting soil acidification induced by nitrification remain unclear. To address this knowledge gap, dissolved biochar fractions (DBC) and solid biochar particles (SBC) were separated and mixed thoroughly with an amended Ultisol. Following a urea addition, the soils were subjected to an incubation study. The results showed that both the DBC and SBC inhibited soil acidification by nitrification. The DBC inhibited soil acidification by decreasing the H+ input from nitrification, while SBC enhanced the soil pHBC. The DBC from peanut straw biochar (PBC) and rice straw biochar (RBC) decreased the H+ release by 16 % and 18 % at the end of incubation. The decrease in H+ release was attributed to the inhibition of soil nitrification and net mineralization caused by the toxicity of the phenols in DBC to soil bacteria. The abundance of ammonia-oxidizing bacteria (AOB) and total bacteria decreased by >60 % in the treatments with DBC. The opposite effects were observed in the treatments with SBC. Soil pHBC increased by 7 % and 19 % after the application of solid RBC and PBC particles, respectively. The abundance of carboxyl on the surface of SBC was mainly responsible for the increase in soil pHBC. Generally, the mixed application of DBC and SBC was more effective at inhibiting soil acidification than their individual applications. The negative impacts of dissolved biochar components on soil microorganisms need to be closely monitored.

[Application effects of biogas slurry partly substituting for chemical fertilizer on autumn tomato production in winter-solar greenhouse]. / æ²¼æ¶²éƒ¨åˆ†æ›¿ä»£åŒ–è‚¥åœ¨æ—¥å ‰æ¸©å®¤ç§‹ç•ªèŒ„ä¸Šçš„åº”ç”¨æ•ˆæžœ.

To explore the effects of biogas slurry coordinating chemical fertilizer on growth promotion of tomato, we used three kinds of typical biogas slurry as concentrated nutrient solution, respectively fermented from raw duck manure, pig manure, cow dung, while urea, monocalcium phosphate and potassium sulphate as auxiliary nutrition to balance the nutrient difference between different dilution ratios of biogas slurry. The results showed the biogas slurry partially substituting chemical fertilizer could significantly improve soil fertility, including available nitrogen, phospho-rus, and potassium. As for water soluble calcium, magnesium, iron, manganese and zinc in soil, biogas slurry application could activate their availability, with the magnitude of such effects depended on the fermentation level of raw materials and dilution ratio. Compared with chemical fertilizer, coordinating biogas liquid fertilizer significantly promoted the growth of tomato, with the yield increased by 55.9%-232.8% and the chemical fertilizer dosage decreased by 18.2%-85.0%. Furthermore, such effects became more prominent along with prolonged time. The fruit quality was significantly improved with the increases of lycopene, ascorbic acid and total sugar, and the decreases of acidity and nitrite concentration, and the decrease of NO2- by 35.6%-90.3%. In addition, the taste flavor of fruits was 7.0%-20.3% higher than that of chemical fertilizer treatment. The yield and quality of tomato took on nonlinear synchronization, and the relation between taste flavor and sugar/acid showed significantly positive correlation, which was affected by fertilizer type. Biogas slurry partly substituting chemical fertilizer could achieve the goals of high yield, high quality, environmental protection, efficient utilization of agricultural resources in tomato production.

Exogenous NO mediated the detoxification pathway of tomato seedlings under different stress of Cu and Cd.

Nitric oxide (NO) is a well-known signaling molecular that plays a significant role in stress tolerance of plants to heavy metals. However, the detoxification mechanism of NO has not been well studied. Here, we examined the absorbing and transporting characteristics of copper (Cu) and cadmium (Cd) in tomato seedlings through nutrient solution culture and its response to exogenous NO under Cu and/or Cd stress. Results showed that Cu and Cd with the concentration of 50 &Mgr;mol·L-1 greatly inhibited plant growth, with Cd having a higher inhibiting effect than Cu. Under single or dual stresses of Cu and Cd, their contents in both tomato roots and leaves were significantly increased. However, tomato roots showed preference to essential element Cu with a luxury uptake and strictly against Cd through cell plasma membrane in which the content of Cd was only one tenth of Cu in plants. These metal stresses, especially Cd stress, could be alleviated by application of exogenous NO. Tomato plants detoxify these passively-absorbed elements through similar mechanisms, including chelation with glutathione, phytochelatin or metallothionein, as well as vascular compartmentalization. Exogenous NO could alleviate these stresses through regulating the oxidation-reduction condition of GSH-GSSH, controlling the metabolism of GSH-PCs, as well as promoting the vascular compartmentalization of excessive Cu and Cd. In addition, NO could induce higher expression of chelators, such as MTs, GSH and PCs, in both roots and shoots, which showed additive effects to other responses and might be another important detoxification pathway mediated through NO for the responses of tomato plants to Cu and Cd stresses.

Alleviating effects of exogenous NO on tomato seedlings under combined Cu and Cd stress.

To investigate the effect of NO on the different origin and regulation of oxidative stress of Cu and/or Cd, tomato seedlings were treated with Cu, Cd, or Cu + Cd in a nutrient solution culture system. The main effect of Cu(2+) was a significant reduction in root activity and nitrate reductase (NR) activity, which was similar to that under 50 µM Cd treatment, but promoted Cu accumulation. The supply of Cu under Cd treatment decreased Cd concentration, while not altered Cu concentration by contrast with Cu treatment, which is suggestive of a replacement of Cu(2+) with Cd(2+) and effective decrease in the boiotoxicity of 50 µM Cd(2+) to tomato seedlings. However, NO alleviated the restriction to NR activity significantly and made the biomass of tomato seedlings recover under Cd treatment, and also increased root activity under Cu and Cu + Cd treatment. Exogenous NO markedly reduced the absorption and transportation of Cu but did not obviously change the translocation of Cd to the aboveground parts under Cu + Cd treatment. Both metals induced lipid peroxidation via the decreasing activation of antioxidant enzymes. The antioxidant enzyme system worked differently under Cu, Cd, or Cu + Cd stress. The activities of peroxidase (POD) and catalase (CAT) were higher under single Cd stress than under the control. Meanwhile, Cu + Cd treatment decreased the activities of POD, superoxide dismutase (SOD), and ascorbic acid peroxidase (APX). Exogenous NO increased POD and SOD activities in the leaves and roots, and CAT activity in the roots under combined Cu and Cd stress. These results suggest that a different response and regulation mechanism that involves exogenous NO is present in tomato seedlings under Cu and Cd stress.

[Effects of NO3- stress on photosynthetic characteristics and nitrogen metabolism of strawber- ry seedlings].

In order to explore the effects of NO3- stress on photosynthetic characteristics and nitrogen metabolism, strawberry seedlings were grown in sand culture condition under different concentrations of NO3- (64, 112 and 160 mmol · L(-1)) with the control of 16 mmol NO3- · L(-1). The results indicated that at the 8th day after treatment, with the increased NO3- concentration, the strawberry leaf net photosynthetic rate (Pn), stomatal conductance (g(s)), PS II actual photochemical efficiency (ΦPS II), PS II maximum photochemical efficiency (Fv/Fm), and photochemical quenching coefficient (q(P)) significantly decreased, and decreased by 67.7%, 68.4%, 35.7%, 23.2% and 26.9%, respectively, when NO3- concentration reached 160 mmol · L(-1) compared with the control. The non-photochemical quenching coefficient (q(N)) increased by 4.4%, 10.9% and 75.8% respectively in the treatments of 64, 112 and 160 mmol NO3- · L(-1) compared with the control. The intercellular CO2 concentration (Ci) decreased under low NO3- concentration stress and then increased under high NO3- concentration stress, while the stomatal limitation (Ls) was vice versa. With the increased NO3- concentration, the nitrate nitrogen, ammonia nitrogen, total nitrogen and Kjeldahl nitrogen contents in the strawberry leaves and roots increased, but the protein nitrogen content decreased. The activities of nitrate reductase (NR) , glutamine sybthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) increased at low NO3- concentration and then decreased at high NO3 concentration. Consequently, the net photosynthetic rate of strawberry seedling leaves decreased, the PS II electron transfer was blocked, the nitrogen accumulated with the increasing NO3- concentration, and the nitrogen metabolism enzyme activity decreased at high NO3- concentrations. When the NO3- concentration reached 64 mmol · L(-1) or higher in the nutrient solution, the growth of strawberry seedlings were inhibited significantly.

The Relationship between Working Conditions and Adverse Health Symptoms of Employee in Solar Greenhouse.

To determine the correlation between the working environment and the health status of employees in solar greenhouse, 1171 employees were surveyed. The results show the 'Greenhouse diseases' are affected by many factors. Among general uncomforts, the morbidity of the bone and joint damage is the highest and closely related to labor time and age. Planting summer squash and wax gourd more easily cause skin pruritus. Asthma-related cough, eye disease, and skin pruritus are significantly correlated with the cultivation of wax gourd. The application of inorganic fertilizer and fertigation dramatically induce the bone and joint damage. The smell of covering film greatly influence skin pruritus. Personal protection is badly scanty and normative occupational health and safety need to be completed.

[Exogenous NO mediated GSH-PCs synthesis pathway in tomato under copper stress].

Nitric oxide (NO), as a biologically active molecule, widely involved in the biotic and abiotic stresses. By using solution culture, this paper reported the dynamic changes in enzyme activity and metabolites related to GSH-PCs synthesis way mediated by exogenous NO in tomato (Lycopersicon esculentum). The results showed that exogenous NO could affect the metabolic pathway of GSH-PCs in tomato seedlings under copper stress. Compared with CK, the activity of γ-ECS and GS was significantly activated, consequently resulting in a sharp rise in GSH and PCs contents in tomato root. Moreover, γ-ECS and GS activity, GSH and PCs contents constantly rise with the extension of processing time under copper stress. Adding exogenous SNP could further improve γ-ECS and GS activity in tomato, and promote the production of GSH and PCs, which contributed to enhancing the ability of removing superoxide and chelating excess Cu2+ to reduce its biological toxicity. To a certain extent, GSH-PCs metabolic changes in leaf lagged behind that in roots. Exogenous BSO could significantly inhibit γ-ECS activity, and applying SNP could significantly reverse the inhibition on GSH and PCs synthesis by BSO. BSO had little effects on PCs content in leaf. Under copper stress, exogenous NO may initiate a signal mechanism and reduce the biotoxicity and oxidative damage caused by excessive Cu2+ by activating or enhancing the enzymatic and non-enzymatic systems in the GSH-PCs synthesis path.

[Effects of exogenous nitric oxide on ascorbate-glutathione cycle in tomato seedlings roots under copper stress].

By using solution culture method, this paper studied the effects of exogenous nitric oxide (NO) on the antioxidants and antioxidases in the ascorbate-glutathione (AsA-GSH) cycle in tomato (Lycopersicon esculentum Mill. ) seedling roots under copper stress.Exogenous NO could affect the metabolic cycle of AsA-GSH in tomato roots under copper stress. Applying appropriate amount of exogenous NO increased the AsA and GSH contents, AsA/DHA and GSH/GSSG ratios, and decreased the DHA and GSSG contents in tomato roots under copper stress. With the addition of 100 micro mol L-1 of BSO, exogenous NO increased the AsA content, AsA/DHA ratio, and the AAO, MDHAR, and DHAR activities, and decreased the DHA, GSH, and GSSG contents and the APX and GR activities. When 250 micro mol L-1 of BSO was added, exogenous NO increased the contents of AsA, GSH, and GSSG, AsA/DHA ratio, and the activities of APX and GR, and decreased the DHA content and the AAO, DHAR and MDHAR activities. It was suggested that exogenous NO could affect the metabolic cycle of AsA-GSH in tomato roots under copper stress, and mitigate the damage of copper stress to tomato roots via regulating the AsA/DHA and GSH/GSSG ratios to alleviate oxidative stress.

[Effects of exogenous nitric oxide on the subcellular distribution and chemical forms of copper in tomato seedlings under copper stress].

A nutrient solution culture experiment was conducted to study the effects of exogenous NO donor (sodium nitroprusside) on the subcellular distribution and chemical form of copper (Cu) in tomato seedlings under the stress of 50 micromol x L(-1) of Cu2+ (CuCl2). Under this stress, the biomass and plant height of tomato seedlings decreased by 33.7% and 23.1%, respectively. Exogenous NO alleviated this inhibition effect significantly, but the Cu concentration and accumulation in the seedling organs still had a significant increase. Under the Cu stress, the Cu concentration and accumulation in the seedling organs were in the order of root > leaf > stem > petiole. Exogenous NO limited the absorbed Cu transferred from root to shoot, but could not remove this translocation. Exogenous NO increased the Cu concentration in vacuole and cell wall significantly, and decreased the Cu concentration in organelle, which lessened the damage of Cu on the regular metabolic balance in cytoplasm and increased the tolerance of organelle against Cu. Exogenous NO increased the acetic acid-extractable Cu (F(HAc)) in root, sodium chloride-extractable Cu (F(NaCl)) in stem, F(HAc) in petiole, and ethanol-extractable Cu (F(E)) and F(NaCl) in leaf, while decreased the concentration and distribution of water-extractable Cu (F(W)) in different organs, which efficiently reduced the bio-toxicity of excessive copper.

[Effects of exogenous nitric oxide on active oxygen metabolism and photosynthetic characteristics of tomato seedlings under cadmium stress].

A hydroponic experiment was conducted to study the effects of exogenous sodium nitroprusside (SNP), a NO donor, on the active oxygen metabolism and photosynthetic characteristics of tomato (Lycopersicon esculentum Mill.) seedlings under Cd stress. The results showed that under the stress, applying 100 micromol x L(-1) SNP promoted the activities of plant superoxide dismutase (SOD) and catalase (CAT) significantly, increased the leaf- and root calcium (Ca) and iron (Fe) contents and the leaf chlorophyll content, net photosynthetic rate (P(n)), transpiration rate (T(r)), and stomatal conductance (G(s)), and decreased the contents of H2O2 and MDA and the concentration of intercellular CO2 (C(i)). The addition of hemoglobin, a NO scavenger, eliminated the effects of SNP, while applying 100 micromol x L(-1) sodium nitrate or nitrite (the decomposition products of NO or its donor SNP) or 100 micromol x L(-1) sodium ferrocyanide (an analog of SNP) had no significant alleviation effects on Cd stress. This study suggested that exogenous NO could promote the scavenging of reactive oxygen, keep the mineral nutrition in balance, and alleviate the damage of Cd stress to the leaf photosynthetic apparatus, making the tomato seedlings preserve their photosynthetic efficiency.