Physiological responses to drought in three provenances of Discorea nipponica Makino

Dioscorea nipponica Makino is an optimal candidate to develop the diosgenin industry in North China. Given the large fluctuations in soil water availability induced by global climate change, information on drought tolerance of this species is urgently needed. Thus, seedlings of three provenances, selected from Manghe, Pangquangou nd Luyashan Nature Reserves in Shanxi Province, were exposed to 70%-85%, 55%-60%, 40%-45% and 20%-35% of water holding capacity, representing normal-watered, light drought stress, moderate drought stress and severe drought stress, respectively. Thirteen indices concerning plant water status, photosynthesis, antioxidants and osmotic regulation were recorded. Principal Component Analysis was applied to identify indices with a high contribution to drought tolerance, fulfilled by the average of subordinate function values (Xij) of drought tolerance index (Xij). We found that rhizome-propagated seedlings of D. nipponica Makino could survive eighty days of severe drought. The drought tolerance of this species is achieved mainly through physiological responses including decreased photosynthesis, increased activity of antioxidant enzymes, and accumulation of osmotic regulating compounds. The means of drought tolerance index for the provenances Manghe, Pangquangou and Luyashan were 0.29, 0.68 and 0.50, respectively. Pangquangou provenance showed higher drought tolerance than the other two, indicating that it might be a good candidate for cross breeding to combat the increasing drought climate in Shanxi Province.