It has been proved that irrigation with high saline water and leaching fraction (LF) affect crop yield, but the effects of irrigation water salinity (ECiw) and LF on fruit quality remain largely elusive. We therefore investigated the effects of ECiw and LF on the yield, fruit quality, and ion content of hot peppers. An experiment using irrigation water with five levels of salinity (ECiw of 0.9, 1.6, 2.7, 4.7, and 7.0 dS·m−1) and two LFs (0.17 and 0.29) was conducted in a rain shelter. The experiment took the form of a completely randomized block design, and each treatment was replicated four times. We increased the salinity of the irrigation water by adding 1:1 milliequivalent concentrations of NaCl and CaCl2 to a half-strength Hoagland solution. The plants were irrigated for 120% and 140% evapotranspiration, corresponding to an LF of 0.17 and 0.29. Results showed that the total fruit yield decreased significantly with an increase in the ECiw as a result of reduction both in the fresh weight of fruit and the number of fruit per plant. An increase in the ECiw also led to a decrease in the total dry biomass of fruit and plant, as well as decreasing water use efficiency (WUEF). Salinity reduced the appearance of the fruit by both decreasing the length (FL) and maximum width (FMW) of the fruit. However, increased ECiw also improved the taste of the hot peppers by increasing the total soluble solid (TSS) content, as well as adding to their nutritional quality with a higher content of Vitamin C (VC). Their storage quality was also improved because of an improvement in the firmness of the fruit (Fn) as well as a reduction in the fruit water content (FWC). An increase in the LF led to an increase in the total fruit yield, total dry biomass of fruit and plant, and WUEF; it also increased the FWC and VC content, and decreased the FMW and fruit shape index (FSI). The threshold-slope linear response and sigmoidal-sharp models were both a good fit for the measured total fruit yield, and the LF had no significant effect on the model parameters. The relative TSS and Fn increased linearly as the electrical conductivity (EC) of soil-saturated paste extract (ECe) increased, whereas they decreased linearly as the relative seasonal evapotranspiration (ETr) increased regardless of the LFs. The relative FW, FL, and FMW decreased linearly with the increased ECe, and increased linearly with the increased ETr regardless of the LFs. The relative fruit Na+ concentration increased linearly as the ECe increased. The regression correlations between the total fruit yield, fruit quality parameters, ion contents, and ECe or ETr could provide important information for salinity and irrigation water management with a compromise between the hot pepper yield and fruit quality.
To study the effects of soil nitrogen (N) fertilization on tea growth, quality and yield, a controlled experiment with green tea [Camellia sinensis (L.) O. Ktze] was conducted. Five N fertilization treatments in soil were designed: 0, 0.97, 1.94, 3.88, and 5.82 g/kg/pot, which were subsequently recorded as N0, N1, N2, N3, and N4. The changes to young shoot biomass, total N and carbon (C), Soil and Plant Analyzer Development (SPAD) value, photosynthetic parameters, senescent characteristics, endogenous hormones, and the quality of green tea leaves were investigated. The results showed that with the increase in N fertilization level, the young shoot biomass, total N and C, SPAD value, net photosynthetic rate (PN), transpiration rate (Tr), stomatal conductance (gS), superoxide dismutase activity, indoleacetic acid, gibberellin, zeatin (ZT), caffeine, and amino acids increased at first and then decreased, the maximums appeared at 3.88 g/kg/pot; whereas the intercellular CO2 concentration (Ci), malondialdehvde contents, abscisic acid (ABA), polyphenol contents, and the ratio of polyphenols (PP) to free amino acid decreased at first and then increased, the minimums appeared at 3.88 g/kg/pot. The immediately significant change in all parameters appeared after 1 month of N treatments. The experiment showed that 3.88 g/kg/pot N fertilization level was the best for growth, quality, and yield of tea, which could provide a theoretical basis for short-term N fertilization management in tea tree.
High temperature and high relative humidity (RH) are one of the most serious agricultural meteorological disasters that limit the production capacity of agricultural facilities. However, little information is available on the precise interaction between these factors on tomato growth. The objectives of this study were to determine the effect of high temperature under different RH levels on tomato growth and endogenous hormones and to determine the optimal RH for tomato seedling growth under high temperature environment. Two high temperature (38/18 °C, 41/18 °C) and three relative humidity (50 ± 5%, 70 ± 5%, 90 ± 5%) orthogonal experiments were conducted, with 28/18 °C, 50 ± 5% (CK) as control. The results showed that the dry matter accumulation of tomato plants under high temperature environment was significantly lower than that of CK. At 38 °C, the dry matter accumulation with 70% relative humidity was not significantly different from that of CK; at 41 °C, dry matter accumulation with 70% and 90% relative air humidity was significantly greater than that of 50%. The concentrations of soluble sugar and free amino acids in all organs in high temperature-treated plants were significantly higher than that in CK. As relative humidity increased, soluble sugar concentrations of each organ decreased, and the free amino acid concentrations increased. Cytokinin (ZT) and indole acetic acid (IAA) concentrations in tomato buds were significantly lower than in CK under high temperature conditions. The lower the RH, the lower the content of ZT and IAA. The gibberellin (GA3) and abscisic acid (ABA) concentrations were higher than in CK under high temperatures. GA3 concentrations decreased and ABA concentrations were augmented with increased humidity. The differences of tomato seedling growth indices and apical bud endogenous hormone concentrations between RHs under high temperature conditions were significant. Raising RH to 70% or higher under high temperature conditions could be beneficial to the growth of tomato plants. The results contribute to a better understanding of the interactions between microclimate parameters inside a Venlo-type glass greenhouse environment, in a specific climate condition, and their effects on the growth of tomato.
In this experiment, the responses of plant growth, gas exchange parameters, and ion concentration to different levels of irrigation water salinity (ECiw of 0.9, 1.6, 2.7, 4.7 and 7.0 dS·m−1) and leaching fractions (LFs of 0.17, 0.29) were investigated in hot pepper plants. The pot experiment was conducted using a completely randomized block design with four replications in a rain shelter. Results showed that the height of the hot pepper plants decreased as the ECiw was increased from 25 d after transplanting (DAT) and increased when the LF was increased from 55 DAT. Neither the ECiw nor the LF influenced the root length. An increase in the ECiw caused the suppression of the stem diameter (SD); leaf length; leaf area; leaf chlorophyll content (CCI); dry biomass of roots, stems, and leaves; net photosynthesis (Pn); stomatal conductance (gS); transpiration rate (Tr); and intercellular CO2 concentration (Ci). An increase in the LF caused the SD, leaf length, leaf area, and dry biomass of stems and leaves to increase. However, the dry biomass of roots and the Pn, gS, Tr, and Ci were not significantly affected by the LF, except for the Ci measured on 23 DAT and the Tr on 76 DAT. The Na+ concentrations in the roots and stems increased, whereas the K+/Na+ ratios decreased as the ECiw increased. An increase in the LF led to a decrease in the Na+ concentration of the roots and stems, whereas there was an increase in the K+ concentration in the stems and the K+/Na+ ratios in the roots and stems. Collectively, an increase in the ECiw had an adverse effect on plant growth and gas exchange and led to the accumulation of the Na+ concentration in the roots and stems, whereas an increase in the LF enhanced plant growth, leaf transpiration, and K+ concentration and reduced the accumulation of the Na+ concentration in the roots and stems. We suggest that higher quantity of water should be applied in higher saline irrigation for satisfactory performance for hot pepper growth.