Influence of Different Root Temperature Treatment on Microstructure of Tomato Leaves

Following the study on effects of different root temperature treatments on growth and stomata of tomato plants under high temperature in summer, the influence of different root temperature treatments on microstructure of tomato leaves was studied in depth in this paper. The tomato plants were cultured with circulating nutrient solutions. Under three different root temperature treatments [（23±1）, （28±1）, （33±1）℃], the microstructure of tomato leaves were observed and measured with paraffin section method. The results showed that with the increase of root temperature, the thickness, palisade tissue thickness, spongy tissue thickness of tomato leaves all decreased, but the epidermis thickness and palisade tissue thickness to spongy tissue thickness ratio increased. Therefore, increased root temperature led to drought stress to tomato plants, and in order to adapt to the hot and drought environment, tomato plants changed their structural characteristics.

Low Root Zone Temperature Exacerbates the Ion Imbalance and Photosynthesis Inhibition and Induces Antioxidant Responses in Tomato Plants Under Salinity

The combined effects of salinity with low root zone temperature （RZT） on plant growth and photosynthesis were studied in tomato （Solanum lycopersicum） plants. The plants were exposed to two different root zone temperatures （28/20℃, 12/8℃, day/night temperature） in combination with two NaC1 levels （0 and 100 mmol L-l）. After 2 wk of treatment, K＋ and Na~ concentration, leaf photosynthetic gas exchange, chlorophyll fluorescence and leaf antioxidant enzyme activities were measured. Salinity significantly decreased plant biomass, net photosynthesis rate, actual quantum yield of photosynthesis and concentration of K＋, but remarkably increased the concentration of Na＋. These effects were more pronounced when the salinity treatments were combined with the treatment of low RZT conditions. Either salinity or low RZT individually did not affect maximal efficiency of PSII photochemistry （Fv/Fm）, while a combination of these two stresses decreased Fv/Fm considerably, indicating that the photo-damage occurred under such conditions. Non-photochemical quenching was increased by salt stress in accompany with the enhancement of the de-epoxidation state of the xanthophyll cycle, in contrast, this was not the case with low RZT applied individually. Salinity stress individually increased the activities of SOD, APX, GPOD and GR, and decreased the activities of DHAR. Due to the interactive effects of salinity with low RZT, these five enzyme activities increased sharply in the combined stressed plants. These results indicate that low RZT exacerbates the ion imbalance, PSII damage and photosynthesis inhibition in tomato plants under salinity. In response to the oxidative stress under salinity in combination with low RZT, the activities of antioxidant enzymes SOD, APX, GPOD, DHAR and GR were clearly enhanced in tomato plants.

Effects of Root Zone Temperature on Growth and Photosynthetic Parameters of Grafted Cucumber

Taking Cucurbita maxima and Cucurbita moschata as root stocks,and‘Jinyou No 3'cucumber as scion,the effects of different root zone temperature conditions optimal temperature(CK)(18-20℃),suboptimal temperature(13-15℃)and low temperature(8-10℃)on the growth and photosynthesis indexes were studied.The results showed that,compared with optimal temperature(CK),suboptimal temperature and low temperature produced a significant inhibition of growth on cucumbers.The plant height,stem diameter,leaf area,number of leaves and dry weight of aboveground part were all reduced,dry weight of underground part and root shoot ratio all increased,while the inhibition was more significant at low temperature.Low and suboptimal temperature conditions also reduced SPAD value,net photosynthetic rate,transpiration rate,intercellular CO_(2) concentration and stomatal conductance of the grafted cucumber.And there were differences between different grafted seedlings,and seedlings with‘black seeds'as stock performed better than those with‘white seeds'as stock at low temperature.

Improved root zone temperature buffer capacity enhancing sweet pepper yield via soil-ridged substrate-embedded cultivation in solar greenhouse

A novel soilless cultivation method,called as soil-ridged substrate-embedded cultivation(SSC)was invented,and an experiment was designed to investigate root zone temperature and production efficiency of sweet pepper cultivated by two SSC patterns,i.e.,SSC-P(polyethylene groove inserted)and SSC-W(wire-mesh groove inserted),and also other two cultivation methods,i.e.,soil ridge(SR)and naked polyethylene groove(PG).Results showed that PG,SSC-P and SSC-W increased the average minimal root zone temperature by 1.01℃,0.75℃,and 1.16℃ compared to SR(16.33℃)during March 16-20,2015.During June 1-5,SSC-P and SSC-W decreased the average maximal root zone temperature by 1.28℃ and 1.29℃ compared to SR(34.99℃),while PG increased it by 1.44℃.PG,SSC-P,and SSC-W decreased the differences of average daytime and night time temperatures by 1.34℃,2.13℃,and 2.88℃ compared to SR(4.56℃)during early stage.However,SSC-P and SSC-W decreased temperature differences of average daytime and night time by 0.9℃ and 1.07℃ compared to SR(0.95℃)during later stage,but PG improved by 2.85℃.Temperature difference of daytime and night time of SSC-W was minimal,and the temperature difference between the diurnal highest and the lowest temperature of SSC-W was also minimal.The buffer capacity of SSC-W was slightly better than that of SSC-P.SSC-W significantly improved the growth of sweet pepper compared to SR.Similarly,fruit yield per square meter of sweet pepper cultivated on SSC-P and SSC-W improved by 21.24%and 50.33%,respectively compared to SR(3.06 kg/m^(2)),while PG lowered the yield by 13.72%.SSC-W was a better SSC pattern compared with SSC-P in terms of production efficiency.