Zengqiang Duan

Use of Spent Mushroom Substrate as Growing Media for Tomato and Cucumber Seedlings

Abstract The aim of this research was to evaluate weathered spent mushroom substrate (SMS), made from spent Flammulina velutipes mushroom substrate, as a growing medium for nursery seedlings. Two vegetable species, cucumber (Cucumis sativus L. cv. Jinchun No. 2) and tomato (Solanum lycopersicum L. cv. Mandy), were grown in 8 media of SMS in various ratios with perlite or vermiculite. A mixed substrate of peat with perlite (1:1; v:v) was used as the control (CK). The experiment was arranged in a completely randomized design under greenhouse conditions. Prior to sowing, some physical and chemical properties of the growing media were determined. Results showed that all the mixtures had desirable physical and chemical properties for their use in nursery tomato and cucumber seedlings except for the T4 (SMS:vermiculite = 1:1; v:v) and the T8 (SMS:perlite = 2:1; v:v) mixtures. Compared with the CK, increased plant height, leaf area, fresh weight, dry weight and index of seedling quality were found in the T3 (SMS:vermiculite = 2:1; v:v) and T6 (SMS:perlite = 4:1; v:v) growing media. SMS should be considered as an alternative for the widely used but expensive and resource-limited peat in greenhouse cultivation.

Effect of CO2 enrichment on the growth and nutrient uptake of tomato seedlings

Exposing tomato seedlings to elevated CO2 concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO2 on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO2 (360 or 720 µL L^(-1)) and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age), and the seedling vigor index (seedling vigor index = stem thickness/(plant height × total plant dry weight) increased with the elevated CO2, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO2 did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO2 treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO2 concentrations.

Low Root Zone Temperature Limits Nutrient Effects on Cucumber Seedling Growth and Induces Adversity Physiological Response

Effects of root-zone temperatures (RZT) (12°C-RZT and 20°C-RZT) and different N, P, and K nutrient regimes on the growth, reactive oxygen species (ROS), and antioxidant enzyme in cucumber seedlings were investigated in hydroponics. Strong interactions were observed between RZT and nutrient on the dry weight (P=0.001), root length (P=0.001) and leaf area (P=0.05). Plant dry weights were suppressed at low RZT of 12°C, while higher biomass and growth of cucumber seedlings were produced at elevated RZT of 20°C under each nutrient treatment. Growth indexes (plant height, internode length, root length, and leaf area) at 12°C-RZT had less difference among nutrient treatments, but greater response was obtained for different nutrients at high RZT. RZT had larger effects (P=0.001) on cucumber seedling growth than nutrients. In addition, N was more effective nutrients to plant growth than P and K under low root temperature to plant growth. Higher hydrogen peroxide (H2O2), malondialdehyde (MDA), soluble sugar (SS) contents in leaves were observed at 12°C-RZT in all nutrient treatments than those at 20°C-RZT, indicating the chilling adversity damaged to plant growth. In general, antioxidant enzyme had larger response under low root-zone temperature. Superoxide dismutase (SOD) activities were higher in both leaves and roots while peroxidase (POD) and catalase (CAT) showed large different action in leaves and roots at both the two root-zone temperature.

Effects of root-zone temperature and N, P, and K supplies on nutrient uptake of cucumber (Cucumis sativus L.) seedlings in hydroponics

The nutrient uptake and allocation of cucumber (Cucumis sativus L.) seedlings at different root-zone temperatures (RZT) and different concentrations of nitrogen (N), phosphorus (P), and potassium (K) nutrients were examined. Plants were grown in a nutrient solution for 30 d at two root-zone temperatures (a diurnally fluctuating ambient 10°C-RZT and a constant 20°C-RZT) with the aerial parts of the plants maintained at ambient temperature (10°C–30°C). Based on a Hoagland nutrient solution, seven N, P, and K nutrient concentrations were supplied to the plants at each RZT. Results showed that total plant and shoot dry weights under each nutrient treatment were significantly lower at low root-zone temperature (10°C-RZT) than at elevated root-zone temperature (20°C-RZT). But higher root dry weights were obtained at 10°C-RZT than those at 20°C-RZT. Total plant dry weights at both 10°C-RZT and 20°C-RZT were increased with increased solution N concentration, but showed different responses under P and K treatments. All estimated nutrient concentrations (N, P, and K) and uptake by the plant were obviously influenced by RZT. Low root temperature (10°C-RZT) caused a remarkable reduction in total N, P, and K uptake of shoots in all nutrient treatments, and more nutrients were accumulated in roots at 10°C-RZT than those at 20°C-RZT. N, P, and K uptakes and distribution ratios in shoots were both improved at elevated root-zone temperature (20°C-RZT). N supplies were favorable to P and K uptake at both 10°C-RZT and 20°C-RZT, with no significantly positive correlation between N and P, or N and K uptake. In conclusion, higher RZT was more beneficial to increase of plant biomass and mineral nutrient absorption than was increase of nutrient concentration. Among the three element nutrients, increasing N nutrient concentration in solution promoted better tolerance to low RZT in cucumber seedlings than increasing P and K. In addition, appropriately decreased P concentration favors plant growth.

Pollutants’ Release, Redistribution and Remediation of Black Smelly River Sediment Based on Re-Suspension and Deep Aeration of Sediment

Heavily polluted sediment is becoming an important part of water pollution, and this situation is particularly acute in developing countries. Sediment has gradually changed from being the pollution adsorbent to the release source and has influenced the water environment and public health. In this study, we evaluated the pollutant distribution in sediment in a heavily polluted river and agitated the sediment in a heavily polluted river to re-suspend it and re-release pollutants. We found that the levels of chemical oxygen demand (COD), NH4+-N, total nitrogen (TN), and total phosphorus (TP) in overlying water were significantly increased 60 min after agitation. The distribution of the pollutants in the sediment present high concentrations of pollutants congregated on top of the sediment after re-settling, and their distribution decreased with depth. Before agitation, the pollutants were randomly distributed throughout the sediment. Secondly, deep sediment aeration equipment (a micro-porous air diffuser) was installed during the process of sedimentation to study the remediation of the sediment by continuous aeration. The results revealed that deep sediment aeration after re-suspension significantly promoted the degradation of the pollutants both in overlying water and sediment, which also reduced the thickness of the sediment from 0.9 m to 0.6 m. Therefore, sediment aeration after suspension was efficient, and is a promising method for sediment remediation applications.

Biomass allocation and organs growth of cucumber (Cucumis sativus L.) under elevated CO2 and different N supply

This article studied the effects of nitrogen (N) and CO2 enrichment on biomass and N accumulation and partitioning of cucumber grown in open top chambers. At the seedling stage, elevated CO2 increased the biomass and N content of the entire plant. The root had the largest increase in biomass and N content among the organs and more biomass allocation. The largest drops of N concentration showed in root at moderate and high N, in leaf at low N, respectively. Elevated CO2 increased stem biomass allocation at moderate and high N, but decreased leaf biomass allocation at all N levels. At the initial fruit stage, the response to elevated CO2 of biomass and N content decreased. Elevated CO2 increased biomass allocation to leaf and resulted in the largest drop of leaf N concentration at low and moderate N supply. High N supply promoted biomass production and N reallocation from the leaf to fruit, but decreased leaf biomass allocation. Thus, biomass allocation is initially affected by root–shoot growth balance to adapt to enriched CO2, leading to the largest root growth, then biomass allocates to another sink (stem). Long exposure of elevated CO2 results in photosynthetic acclimation in deficient N supply, which probably attributes to excessive stem and leaf biomass allocation and shortage of fruit storage. But high N shifts biomass allocation from leaf to fruit. Practically, sufficient N supply is needed for an efficient transport of carbohydrates to fruits and increases the yields under elevated CO2.

The relationship between root exudation properties and root morphological traits of cucumber grown under different nitrogen supplies and atmospheric CO 2 concentrations

AimsNitrogen supply and atmospheric CO2 concentration ([CO2]) could influence root exudates directly by altering compound concentrations in roots and indirectly by regulating root morphology. This study assessed these direct and indirect effects on cucumber root exudation.MethodsCucumber roots with various morphological traits were obtained in different combinations of nitrogen supplies and [CO2] treatments. Then, the correlations between ten compounds in root exudates and their concentrations in root extracts as well as root morphological traits were evaluated.ResultsIn case of root exudates, the amounts of sugars were more closely correlated to the root surface area, whereas organic acids and amino acids were more closely associated with the number of root tips. Moreover, fructose, glucose, sucrose and oxalic acid in root exudates were correlated to their concentrations in root extracts, whereas there was little correlation between root exudates and extracts for malic acid, citric acid or four amino acids.ConclusionsSugars were probably released from the whole roots by passive or facilitated diffusion, so both the direct and indirect effects were important. Organic acids and amino acids were mainly secreted from the root apices by active transport, thus the indirect effect was more important.

Effects of Elevated CO2 on Nutritional Quality of Vegetables – A Review

Elevated atmospheric CO2 (eCO2) enhances the yield of vegetables and could also affect their nutritional quality. We conducted a meta-analysis using 57 articles consisting of 1,015 observations and found that eCO2 increased the concentrations of fructose, glucose, total soluble sugar, total antioxidant capacity, total phenols, total flavonoids, ascorbic acid, and calcium in the edible part of vegetables by 14.2%, 13.2%, 17.5%, 59.0%, 8.9%, 45.5%, 9.5%, and 8.2%, respectively, but decreased the concentrations of protein, nitrate, magnesium, iron, and zinc by 9.5%, 18.0%, 9.2%, 16.0%, and 9.4%. The concentrations of titratable acidity, total chlorophyll, carotenoids, lycopene, anthocyanins, phosphorus, potassium, sulfur, copper, and manganese were not affected by eCO2. Furthermore, we propose several approaches to improving vegetable quality based on the interaction of eCO2 with various factors, including species, cultivars, CO2 levels, growth stages, light, O3 stress, nutrient, and salinity. Finally, we present a summary of the eCO2 impact on the quality of three widely cultivated crops, namely, lettuce, tomato, and potato.