Plastic Shed Research Articles

Effects of exogenous sulfur on maize (Zea mays L.) growth and Cd accumulation in Cd-contaminated plastic shed soil.

Cadmium (Cd) pollution in plastic shed soils has become increasingly severe, posing a great threat to human health and social stability. Phytoremediation of cadmium pollution is an environmentally friendly and inexpensive remediation method. In this study, maize (Zea mays L.) was selected as the phytoremediation crop by a potted method, and the bioavailability of cadmium was investigated by adding exogenous elemental sulfur. The relationships among the sulfur content, maize growth, cadmium accumulation, and soil parameters were systematically studied. The results showed that, with the supplement of sulfur, the soil pH and activities of soil enzymes (urease, catalase, and sucrase) decreased gradually, and the available heavy metals (Cd, Cr, Zn, and Cu) in soil showed an upward trend. The optimal cadmium enrichment was achieved under T2 by increasing both the biomass of the maize plant and the cadmium concentration in roots and stems. However, T3 and T4 significantly inhibited the growth of maize roots and shoots, leading to a much lower plant biomass compared with that of CK (sulfur-free treatment) and T2. In addition, the cumulative cadmium was not increased because of the low accumulation of cadmium in some parts of the plant. Correlation analyses showed that the sulfur content was negatively correlated with soil pH and maize biomass (P < 0.01), and the cadmium content of whole maize was positively correlated with the dry weight of maize (P < 0.05) and the cadmium content in roots and stems (P < 0.01). In summary, to optimize cadmium phytoremediation of the plastic shed soil, an appropriate concentration of sulfur should be selected in practical applications to ensure that the biomass of the maize is maximized, and the cadmium concentration in different parts of the maize is increased or stabilized.

Comparative study on the pollution status of organochlorine pesticides (OCPs) and bacterial community diversity and structure between plastic shed and open-field soils from northern China

The pollution status of organochlorine pesticides (OCPs) and microbial community in plastic shed and open-field soils may be different due to the significant variations in environmental factors between the two cultivation modes. However, the differences remain unclear. We conducted a regional-scale survey to investigate the pollution level, distribution, and sources of 20 OCPs, and to evaluate the soil physicochemical properties and bacterial community in soils from plastic shed and open-field locating the north areas of China. We found that levels of total OCPs in the plastic shed soils were significantly higher than those in the nearby open-field soils. Most of these OCPs were attributed to historical application, except for dichlorodiphenyltrichloroethanes (DDTs) due to the fresh input along with dicofol application. Soil pH (for both cultivation modes) and total organic carbon (TOC) content (only for plastic sheds) were significantly correlated with the total OCP concentrations. Additionally, microbial diversity and richness were generally lower in plastic shed soils than in nearby open-field soils for each region. The bacterial community variation among different regions might be principally determined by the soil type. Soil pH had the greatest impact on the microbial community across all plastic shed and open-field samples. These results provide a better understanding of the environmental impact and ecological risk of OCPs in soils with different cultivation modes.

Soil N transformation rates are not linked to fertilizer N losses in vegetable soils with high N input

Vegetable soils under plastic shed are characterized by multiple cropping and extremely high rates of nitrogen (N) application, but the N use efficiency (NUE) is generally low and the rate of N loss is often high. The underlying mechanisms behind these N losses following long-term N fertilizer applications remain elusive. Here, a 15N tracing incubation study in conjunction with in-situ monitoring was performed to investigate the effects of different N fertilization regimes on gross N transformations, microbial abundance and N losses via NO3− leaching and N2O emissions in a vegetable soil under plastic shed subjected to 14 years of repeated N fertilization. The field experiment comprised of six treatments: no N fertilization (control, CK), and applications of chicken manure (M), chemical N plus M (CM), CM plus straw (CMS), 42 % of chemical N plus chicken manure (RCM) and RCM plus straw (RCMS). The results showed that the total gross N mineralization rates were significantly higher in CMS, RCMS and M treatments than in CK, CM and RCM treatments. The total gross NH4+ immobilization rates followed the order of CK > CM > CMS > M > RCM ≈ RCMS, indicating a decreasing NH4+ immobilization rate after N application. Gross autotrophic nitrification rate was significantly enhanced by fertilizer application in the order: CK < CM < CMS ≈ RCM < M < RCMS, mainly due to both increased mineralization rates and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB). A significant negative relationship between gross rates of NH4+ immobilization and autotrophic nitrification suggests that higher autotrophic nitrification decreased NH4+ immobilization. Reduced chemical N input alleviated soil acidification, NO3− leaching and N2O emissions. There were significant positive relationships between rates of chemical N input and N loss but no relationships between gross N transformation rates and tomato yields, NO3− leaching losses and N2O emissions. Thus, soil N transformation rates do not reflect rate of fertilizer N losses in vegetable soil managed under plastic shed. We thus suggest that chemical N application rate could be reduced to decrease N losses while sustaining vegetable production.

Schedule of drip irrigation under film for watermelon growth in plastic shed based on E601-B pan evaporation in northwest China

In order to find the optimum drip irrigation schedule for watermelon grown in plastic sheds using E601-B type pan evaporation, effects of different water supply conditions (Kcp: 0.5, 1.0, 1.5 Ep) on growth, photosynthesis, fruit yield, and water use efficiency during different growth stages were studied. The relationship between irrigation water amount (Ir), evapotranspiration (ET), and yield was also analysed. Results showed that treatment 5 (T5) performed best. The recommended corresponding irrigation K(cp)s were 1.00, 1.00, 1.50, and 1.00 for seedling, flowering and fruit bearing, fruit development, and fruit mature stages, respectively. For T5, the ratios of plant evapotranspiration to pan evaporation (ET/Ep) during the four stages were 0.40, 0.76, 1.59 and 0.77, respectively. Both irrigation water amount and ET positively correlated to fruit yield and plant fresh weight (FW). For FW, the correlation coefficients were 0.79, 0.64, 0.80 and 0.50 (P<0.05), respectively. There were no correlations between plant dry weight (DW) and irrigation water amount or evapotranspiration. The data from this study provide reference information for precision management and scientific irrigation on watermelon.

Effect of High Temperature on Photosynthetic Capability and Antioxidant Enzyme Activity of Flag Leaf and Non-leaf Organs in Wheat

Winter wheat in North China has been subject to high temperature stress during grain filling. The purpose of this study was to determine the effect of high temperature on the photosynthetic capability of flag leaf and the antioxidant system of flag leaf and non-leaf organs in winter wheat cultivars Shijiazhuang 8(tolerant to high temperature) and Henong 341(sensitive to high temperature). High temperature(HT) stress was imposed with a plastic shed from the 8th to the 22 nd day after anthesis, and normal temperature was used as the control. Under HT, the photosynthetic rate and chlorophyll content of flag leaf decreased by 18.7%–24.9% and 5.7%–6.2%, respectively; whereas the malodialdehyde(MDA) and proline(Pro) contents in flag leaf blade, sheath, peduncle, glume and grain increased in different levels. The increased percentage of MDA was higher in flag leaf than in non-leaf organs and that of Pro was higher in non-leaf organs than in flag leaf. Superoxide dismutase(SOD) in flag leaf, glume and grain, catalase(CAT) in flag leaf, sheath and grain, and peroxidases(POD) in flag leaf, sheath and glume were induced at early stage(4 d after treatment) by HT treatment, while the activities of antioxidant enzymes in other organs increased at later stage(7 d after treatment). Thereafter, the activities of antioxidant enzymes in various organs maintained lower levels compared with those of the control. At the 26 th day after anthesis when HT stress was relieved for four days, the SOD activity in sheath, peduncle and glume and the POD activity in flag leaf, glume and grain began to increase, but the effects of HT on the SOD and POD activities in other organs and the CAT activity in all organs seemed irreversible. In general, the non-leaf organs exhibited higher antioxidant capability and heat tolerance than flag leaf. Compared with Henong 341, Shijiazhuang 8 exhibited higher cell membrane stability and antioxidant activity in leaf and non-leaf organs, leading to a tolerance to HT stress of the whole plant. This might be the physiological basis of smaller percentage of yield loss in Shijiazhuang 8 than in Henong 341 under HT stress. Our results indicate that non-leaf organs of wheat play an important role in adaptability to climate warming.

Effects of Salt Stress on Growth, Ion Concentration, and Quality of Pineapple Fruits

This work was aimed to investigate the growth, ion contents, quality, and aroma components of pineapple fruits as affected by salinity stress. Pot experiments with four levels of salinity [0, 0.25%, 0.50%, and 0.75% sodium chloride (NaCl)] and eight replications were conducted in a plastic shed. The results suggested that the transverse diameter and longitudinal diameter as well as weight per fruit of pineapple fruits declined with increasing salinity. Salt stress caused the increasing of sodium (Na+). Salt stress resulted in the significant decreasing of potassium (K+)/Na+ and calcium (Ca2+)/Na+ with decreasing contents of K+ and Ca2+. Salt stress slightly affected the chemical quality of pineapple fruits. The firmness of fruit was significantly decreased. The total relative content of ester aroma components was increased by lower salt stresses at 0.25% and 0.50% and was decreased by high salt stress at 0.75%. The characteristic aroma component was not identified in the salt-stressed fruits.

RECENT STATE IN STRAWBERRY PRODUCTION AND RESEARCH IN CHINA

China has become the largest country in strawberry production in the world. The main culture types are the green house, open field, large and small plastic shed. The most popular cultivars are 'Toyonoka' and 'Allstar'. The new strawberry cultivars have been protected in China. Public strawberry breeding programs have been conducted in several provinces and cities. Researches in physiology, biotechnology and wild germplasm in strawberry have been conducted in many colleges and institutes in China.

Apoptosis in a tissue-like culture model of human colorectal adenoma cells

Tissue-like cultures of LT97 human colonic adenoma cells were produced by plating on reconstructed connective tissue supports (CTR) containing colon-associated fibroblasts to form mucosal monolayers and polyp-like structures closely resembling the in vivo situation. Tight cell–cell contacts and a high density of desmosomes were observed in 93.8 ± 3.5% of the section area for CTR cultures, but only in 17.8 ± 10.0% of the area for cultures on collagen gels (CG) without fibroblasts. While LT97 cultures on plastic shed apoptotic bodies into the medium, they collected at the basal pole of the cell layer in the CTR cultures as is also observed in adenoma tissue. Only a small proportion was released into the medium as shown by the detection of apoptosis specific keratin fragments, which could be increased by 100 μM of quercetin and resveratrol. In addition, tissue-like structures altered the relative effectivity of test compounds. As the tissue-like conditions closely resemble the situation in vivo tissue-like cultures are an important step towards the establishment of tissue reconstructs that can replace animal models in the analysis of basic mechanisms of growth control and the testing of tumor promoting and chemopreventive compounds and may even be superior in terms of predictivity as they use human cells.

Solar energy utilisation efficiency in environment-controlled agriculture in China

In the light of an analysis of the solar radiation and temperature resources in different part of China, this paper classifies Environment-Controlled Agriculture (ECA) in China into zones and briefly introduces the feature of each zone. Meanwhile, features of different ECA types such as heliogreenhouse, plastic arched shed, adumbral net and their contributions to increasing solar energy utilisation efficiency are analysed. On the basis of the above analysis, possible technical ways to increase potential production of ECA are put forward.