| In order to make full use of the light resource in northern China, the objective of this paper was attempting to relieve the high temperature stress through increasing the air humidity to achieve anniversary production of greenhouse tomato.Experiments were carried out in growth chamber with natural light(150cm ×120cm ×200cm)from June to October in 2014. During the period of 10:00～16:00 each day, tomato plants were treated with relative humidity of RH:30%～40% (L) for comparison, RH 60%-70% (M), RH 80%-90% at temperature 32-35℃. To studied the effect of different humidity under high temperature on tomato morphological, physiological and biochemical and reproductive growth, the conclusions were as follows:Under the high temperature (32℃～35℃), increasing the humidity of the air did not obviously effect the development of tomato leaf number, but compared with control group L, plant height, stem diameter and leaf length in high humidity treatment group H were increased by 0.8%～17.2%,7.6%～13.1% and 15.5%～18.5%. At the end of the treatment, compared with control group L, in high humidity treatment group H, SOD activity of leaf was increased by 24.2%～48.1%, POD activity and MDA content of leaf were decreased by 25.7%～38.0% and 16.7%-25.0%. The Pro content and cell membrane relative permeability of variety "hong tu" in humidity treatment H group were decreased by 80% and 42.7% than those in control group L in the second test, the result indicated that the plants were continually adjusting and adapt through itself under different air humidity. The chlorophyll content was the lowest in control group L, and the same performance of different varieties was got.From the observation of 2nd to 4th truss of tomato plants, under the high temperature(32℃-35℃), the results showed that:the flowering rate and fruit-set rate of 2nd to 4th truss in treatment H increased by 8.3%～29.4%,13.6%～49.1%; 19.1%～35.1%,23.5%～53.2% and 23.8%～37.7%,46.7%～55.9%; the pollen vigor increased by 38.1%～44.6%,50.4%～54.8% and 52.1%-56.9%, respectively. Due to the time continuing of high temperature and consumption of nutrient, the pollen vigor of 4th truss only was 10.4%～37.7% that of 2nd truss, as well the same performance of different varieties was got. Pollen grain surface morphology observed under scanning electron microscopy, high temperature stress make pollen grain surface shrinkage, increasing the air humidity can reduce the number of the pollen grains. Through tissue culture vitro of pollen, the results showed that:with the time continuing of high temperature(32℃-35 ℃), increasing the air humidity can slow down the fall of pollen vigor.Based on the leaf temperature and leaf-air temperature under different humidity treatment, the result showed as follows:under the high temperature, increasing humidity can decrease leaf temperature. The leaf-air temperature difference in H humidity treatment is -3～0℃, and the plant is vigorous. Thus, base on the leaf-air temperature difference, increasing the humidity can improve the tomato plant growth..In conclusion, under the high-temperature period (10:00-16:00) in greenhouse to increase the air humidity to 80%-90% can promote vegetative growth and reproductive growth of tomato plants, and high humidity can help tomato plants continually adjusting and adapt through itself, to relieve adversity persecution. However, in terms of leaf temperature change, treatment M is more suitable. Therefore, increase air humidity under the high temperature can effectively help relieve the damage of high temperature. |
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