Physiological responses of orchid pseudobulbs to drought stress are related to their age and plant life form
As storage organs for water and nutrients, pseudobulbs play an important role in the survival of orchids. However, the differences in morphological and physiological responses of pseudobulbs to drought stress between epiphytic and terrestrial orchids remain undefined, and little is known about the physiological imparity of different-aged pseudobulbs. We investigated the anatomy and changes in physiology of pseudobulbs in an epiphytic orchid (Cymbidium tracyanum) and a terrestrial orchid (C. sinense) and compared their responses and recovery during and after periods of drought stress. In particular, “ramets severance treatment” and “multiple leafless pseudobulbs treatment” were applied for C. tracyanum to verify the utilization strategy for the stored water. When compared with C. sinense, the pseudobulbs of C. tracyanum have larger water-storage cells and higher water content, and the enhanced water storage of C. tracyanum can be used and recovered more rapidly. And they had more flexibility in shifting stored nonstructural carbohydrates. The remarkably high concentration and different change trends of abscisic acid (ABA) between different-aged pseudobulbs under drought stress were only found in C. tracyanum. When pseudobulb age was considered, the stored water and carbohydrate changed more rapidly in the youngest pseudobulbs of both species in response to stress. Our results indicated that the pseudobulbs differ in their means for coping with drought conditions according to their life form and age. These findings contribute to our understanding about the functional diversification of pseudobulbs and their strategies for ecological adaptations.
KeywordsPseudobulb Orchid Drought Epiphytic Terrestrial
The authors are grateful to Dr Jia-lin Huang (Key Laboratory for Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China) for his help in the preparation of our experimental materials. And our research was financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB3101), the National Natural Science Foundation of China (31670342) and the CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Science (09KF001B04).
- He J, Norhafis H, Qin L (2013) Responses of green Leaves and green pseudobulbs of CAM orchid Cattleya laeliocattleya Aloha case to drought stress. J Bot 2013:9Google Scholar
- Liu Z, Chen L, Liu K, Li L, Zhang Y, Huang L (2009) Climate warming brings about extinction tendency in wild population of Cymbidium sinense. Acta Ecol Sin 29:3443–3455Google Scholar
- Lu HZ, Liu WY, Yu FH, Song L, Xu XL, Wu CS, Zheng YL, Li YP, Gong HD, Chen K, Li S, Chen X, Qi JH, Lu SG (2015) Higher clonal integration in the facultative epiphytic fern Selliguea griffithiana growing in the forest canopy compared with the forest understorey. Ann Bot 116:113–122CrossRefGoogle Scholar
- Luo Y, Jia J, Wang C (2002) A general review of the conservation status of Chinese orchids. Chin Biodivers 11:70–77Google Scholar
- Seifter S, Dayton S, Novic B, Muntwyler E (1949) The estimation of glycogen with the anthrone reagent. Biochemistry 25:191–220Google Scholar
- Zhang SB, Dai Y, Hao GY, Li JW, Fu XW, Zhang JL (2015) Differentiation of water-related traits in terrestrial and epiphytic Cymbidium species. Front Plant Sci 6:260Google Scholar