The effect of cold stress on endogenous hormones and CBF 1 homolog in four contrasting bamboo species

An unusually severe snow disaster in southern China in 2008 exposed variation among different species of bamboo: some species were highly tolerant to low-temperature damage, but some suffered extensive damage or death. Therefore, this study was conducted to determine the effects of cold stress on endogenous hormones and the expression of homologs of CBF ₁ in four bamboo species differing in their tolerance to cold. All four bamboo species were subjected to cold stress with a temperature gradient (10, 5, 0, −5, and −10°C), and each low temperature treatment was maintained for 48 h. Results showed that ABA, GA₁, and GA₄ were significantly affected by cold stress: ABA increased with cold stress in all species, while GA₁ and GA₄ reduced with cold stress. ABA levels and the ratio of ABA/(GA₁ + GA₄) in leaves of Neosinocalamus affinis and Bambusa rigida were both higher than those of hybrid bamboo (Bambusa pervariabilis × Dendrocalamopsis grandis) and Dendrocalamus latiflorus for all treatments, while GA₁ and GA₄ were conversely lower as compared to the hybrid variety and D. latiflorus. Moreover, CBF ₁ homolog was up-regulated during cold stress, with higher expression levels in the leaves of cold-tolerant species than cold-sensitive ones. Results revealed that high levels of ABA and CBF ₁ , as well as the ABA/GA_s balance, are important in increased plant resistance to cold stress.