Free proline, total soluble sugar enrichment, photosynthetic abilities and growth performances in dragon fruit (Hylocereus undatus (Haw) Britt. & Rose) grown under mannitol-induced water deficit stress
2018
Tisarum, R. | Samphumphung, T. | Theerawitaya, C. | Cha-um, S.
Pitaya or dragon fruit is a tropical climbing cactus, being used as agronomic fruit crop in Southeast Asia, especially in Vietnam, Thailand and China. It has been identified as a drought-tolerant crop that can overcome water shortage but needs water supply in the flowering, fruit development stages and in the dry season. In general, the loose soil properties and 3-7 days irrigation is required for the optimum growth and development of pitaya fruit species. The objective of the present study was to investigate the biochemical, physiological and morphological responses of pitaya plantlets to mannitol-induced water deficit stress. Osmotic potential in the phylloclades of in vitro photoautotrophic plantlets dropped depending on the concentration of mannitol-added medium, leading to free proline and total soluble sugar accumulation. Chlorophyll a and chlorophyll b in the phylloclades, being sensitive to mannitol-induced water deficit (50 mM mannitol), degraded by 53.8 and 56.6%, respectively, thus inhibiting the net photosynthetic rate. Shoot height and fresh weight of phylloclades were significantly inhibited by 15.0 and 29.8%, respectively, when subjected to 50 mM mannitol medium. In summary, free proline and total soluble sugar were enhanced, whereas photosynthetic abilities were declined in pitaya plantlets in response to mannitol-induced water deficit.
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