Exogenous Spermidine Alleviated Waterlogging Damages in Two Varieties of Camellia oleifera

Abstract

The potential management of waterlogging-damaged plants can be through the promotion of aliphatic polyamine accumulation, such as spermidine (SPD), in non-accumulator and accumulator species under stress. Camellia oleifera, commonly called tea oil, is an evergreen shrub confronting waterlogged soils in Hainan forest plantations during the pluvial season. As far as we know, few studies focused on the responses of C. oleifera to abiotic stresses, such as waterlogging (WL), and the involvement of SPD in WL tolerance remains unclear. Therefore, two cultivars of C. oleifera (CoH1 and CoH2) were subjected to WL and exogenous SPD to shed light on the role of SPD on WL tolerance via the morphological and physio-biochemical responses of C. oleifera under stress. The results showed that the two varieties of C. oleifera were sensitive to WL stress, and spraying SPD enhanced WL tolerance via root activities, photosynthesis, redox-homeostasis, antioxidant machinery, and compatible solute components. Thus, exogenous SPD significantly reduced the damages caused by WL in C. oleifera seedlings. Moreover, the alternative oxidase (AOX) protein content was down regulated by WL in both varieties of C. oleifera, whereas exogenous SPD enhanced the AOX protein under stress. The two varieties of C. oleifera generally had similar morphological and physiological responses to WL. However, CoH2 demonstrated better photosynthesis compared to CoH1. The results of the present study provide a significant outlook to improve the accumulation of SPD in trees under abiotic stress, particularly via genome editing techniques.