Effects of PEG Drought Stress on Photosynthetic System of Phalaenopsis pulcherrima

doi:10.3969/j.issn.1000-2561.2021.09.028

Abstract

Abstract:

Three year old tissue culture seedlings of Phalaenopsis pulcherrima were treated with 5%, 10% and 20% PEG 6000 solution respectively to study the effects of drought on photosynthetic system. Drought led to the decrease of stomatal density, opening and length, and the decreasing trend became more obvious with the prolongation of PEG stress time. More than 10% treatments were significantly different from CK. With the extension of PEG treatment time, the decline trend of malic acid content was slowed down. The content of malic acid in leaves measured in the early morning was significantly higher than that in the evening. After 15 days of treatment, the difference of malic acid content between PEG 20% treatment and CK was significant, which was 27.16% lower than that of CK. The net photosynthetic rate, transpiration rate and stomatal conductance of leaves decreased gradually with the prolongation of PEG stress time. The change of intercellular CO₂ concentration showed an opposite trend, and water use efficiency increased first and then decreased. After 15 days of treatment, the difference between the treatment of PEG 5% and CK was significant. Drought caused the initial fluorescence value (F_o) to increase gradually, but the variable fluorescence value (F_v), maximum fluorescence value (F_m), PSⅡ actual photochemical efficiency (F_v/F_m), PSⅡ potential photochemical efficiency (F_v/F_o) decreased gradually. The apparent electron transfer rate (ETR), photochemical quenching coefficient (qP), and PSⅡ actual quantum efficiency (Yield) decreased with the increase of PEG stress. The non photochemical quenching coefficient (NPQ) increased significantly with the increase of PEG stress concentration. After 15 days of treatment, the difference between the treatment of PEG 5% and CK was significant. Conclusion: 10%, 20% PEG treatment could reduce photosynthesis and inhibit the synthesis of malic acid by affecting stomatal closure and stomatal density of leaves in a short period of time. At the same time, it affected the absorption and transmission of light energy and photochemical conversion in leaves of P. pulcherrima. 5% PEG treatment did not show the phenomenon of inhibition of photosynthetic physiology until 10 days after treatment, indicating that moderate and severe drought could be achieved in a short time. The stomatal characters of leaves were affected, and the photosynthetic capacity of leaves was reduced. Finally, the synthesis of photosynthetic products was blocked, and the photosynthetic system was inhibited under drought stress.

Key words: Phalaenopsis pulcherrima, PEG stress, photosynthetic characteristics, malic acid

CLC Number:

S682.31

ZHANG Han, LI Han, CHEN Qi, YANG Fusun. Effects of PEG Drought Stress on Photosynthetic System of Phalaenopsis pulcherrima[J]. Chinese Journal of Tropical Crops, 2021, 42(9): 2645-2652.

Figures/Tables 5

Fig. 1 Effect of PEG stress on stomatal parameters of P. pulcherrima Different lowercase letters indicate significant difference (P<0.05).

Fig. 2 Effect of PEG stress on malic acid content of P. pulcherrima leaves

Fig. 3 Effect of PEG stress on photosynthetic physiology of leaves of P. pulcherrima

Fig. 4 Effect of PEG stress on fluorescence characteristics of leaves of P. pulcherrima

Fig. 5 Changes of fluorescence characteristics of P. pulcherrima leaves under PEG stress with photosynthetic effective radiation on 15th day

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