Effect of increasing humidity on flowering, fruit-setting and pollen characteristics of tomato under heat stress
In order to make full use of the light resource and extend the growing period over summer in northern China, tomato plants (Lycopersicon esculentum Mill.) were grown in three growth chambers (150×120×200 cm) with relative humidity of 30-40% (L, as control), 60-70% (M), and 80-90% (H), in an attempt to relieve the stress caused by high temperature (32-35°C) during summer. The growth chambers were covered with transparent plastic film and natural radiation could be transmitted. Relative humidity was controlled at around 10:00-16:00 during the day in the experiment. The 2nd, 3rd and 4th flower clusters of tomato plants that developed during the experimental period were observed. The results showed the following: i) pollen viability in treatment H increased by 38-45, 50-55 and 52-57%, respectively, for the 2nd, 3rd and 4th flower cluster compared with that of treatment L; ii) pollen viability of the 4th flower cluster was only 10-38% that of the 2nd flower cluster. Furthermore, the surface of pollen grains in treatment L was shrunken, as observed under the scanning electron microscope. Increasing air humidity in treatment H might reduce the numbers of shrunken pollen grains by up to 76%. By pollen culture in vitro, it was found that the decrease in pollen viability was slowed down with increasing time at high temperature (32-35°C) for treatment H. Finally, the rates of flowering and fruit-setting were increased by 18 and 37% in treatments H and M, respectively. It was concluded that increasing humidity under conditions of high temperature (32-35°C) and dry climate could effectively increase the rate of flowering and fruit setting.
Wang, S.S., Li, Y.L. and Wen, X.Z. (2018). Effect of increasing humidity on flowering, fruit-setting and pollen characteristics of tomato under heat stress. Acta Hortic. 1227, 305-312
tomato, heat stress, air humidity, pollen grain