Abstract:

Drought stress is an important factor affecting plant growth and development. When plants are in drought stress, they also make some changes to adapt to the environment. This study used ‘Zihonglong’ as the experimental material, a variety of pitaya widely planted in guizhou. In order to lay a theoretical foundation for the physiological research of pitaya, the adaptability of pitaya to drought was evaluated by studying its stem and root growth, stem water content, stomatal movement, leaf temperature change and chlorophyll synthesis. The relative water content in the stem of pitaya was slightly decreased (80%) in drought treatment lasted 16 weeks in soil moisture content 15%. The drought treatment significantly promoted the growth and elongation of new roots, but limited stem elongation and crosswise. Under drought treatment, the stomatal open frequency, stomatal apertura, stomatal size, and stomatal density were lower than those in the control. New stems of pitaya were more sensitive to temperature increase or decrease than mature stems, and the stem surface temperature of drought treatment was higher than that of the control. With the degree of drought, the photosynthetic pigments decreased significantly, and the chlorophyll fluorescence parameters changed. The pitaya stem had strong water retention capacity and was highly resistant to drought. Under drought, the water of pitaya fruit was preferred to providing to the root system to promoting root growth, maintaining stem elongation and growth, while crosswise was inhibited. Under mild and moderate water stress, the photosynthetic capacity of the stem of pitaya did not decrease significantly, while under severe water stress, the photosynthetic efficiency was significantly affected.

Key words: Hylocereus undatus, drought resistant, adaptation