以牡竹属(Dendrocalamus Nees)的清甜竹(D.sapidus Q.H.Dai et D.Y.Huang)、花吊丝竹〔D.minor var.amoenus(Q.H.Dai et C.F.Huang)Hsueh et D.Z.Li〕和勃氏甜龙竹〔D.brandisii(Munro)Kurz〕盆栽苗为实验材料,测定了模拟低温(0℃、-5℃、-10℃、-15℃、-20℃和-25℃)条件下3个竹种离体叶片的相对电导率和伤害率,在此基础上根据Logistic方程推算出3个竹种的低温半致死温度(LT50);对自然低温(15℃、10℃、5℃、3℃、0℃和-2℃)条件下3个竹种叶片的形态变化以及相对电导率、叶绿素和MDA含量及SOD活性的变化也进行了比较分析。结果表明:在模拟低温条件下,3个竹种离体叶片的相对电导率和伤害率均随温度降低逐渐增大,且总体上与对照(25℃)有显著差异(P<0.05);根据Logistic方程推算出花吊丝竹、勃氏甜龙竹和清甜竹的LT₅₀分别为-3.07℃、-1.83℃和-1.40℃。在日最低温度大于5℃的自然低温条件下3个竹种的叶片均能够正常生长,而随温度降低,叶片逐渐出现水浸斑点、失绿等症状直至干枯脱落,其中清甜竹叶片伤害症状最重;在自然低温条件下,随日最低气温的降低,3个竹种叶片的叶绿素含量总体呈下降趋势、相对电导率则逐渐升高、MDA含量和SOD活性总体上均呈波动的趋势;与日最低气温15℃相比,在日最低气温-2℃条件下清甜竹叶片叶绿素含量和SOD活性降幅最大而花吊丝竹降幅最小,清甜竹叶片相对电导率最高而花吊丝竹最低。根据LT₅₀和叶片形态及生理指标的变化,可确定3个竹种的抗寒性均较差,其中清甜竹的耐寒能力最弱。 

Taking pot seedlings of three species in Dendrocalamus Nees including D． sapidus Q． H． Dai et D． Y． Huang， D． minor var． amoenus ( Q． H． Dai et C． F． Huang) Hsueh et D． Z． Li and D．brandisii ( Munro) Kurz as experimental materials， the relative electric conductivity and damage rate of in vitro leaf of three species under simulated low temperature conditions ( 0 ℃ ， -5 ℃ ， -10 ℃ ，-15 ℃ ，-20 ℃ and -25 ℃ ) were determined， and on this basis， their semilethal low temperatures ( LT₅₀) were calculated according to Logistic equation． And leaf morphological change and changes of relative electric conductivity， contents of chlorophyll and MDA， and SOD activity in leaf of three species were also compared and analyzed under natural low temperature conditions ( 15 ℃ ， 10 ℃ ， 5 ℃ ， 3 ℃ ， 0 ℃ and -2 ℃ ) ． The results show that under simulated low temperature conditions， relative electric conductivity and damage rate of in vitro leaf of three species all increase gradually with decreasing of temperature， and generally have significant difference ( P＜0． 05) with those of the control ( 25 ℃ ) ． According to Logistic equation， LT50 of D． minor var． amoenus， D． brandisii and D． sapidus calculated is -3． 07 ℃ ，-1． 83 ℃ and -1． 40 ℃ ， respectively． Under natural low temperature conditions with daily minimum temperature higher than 5 ℃ ， three species leaves all grow normally， but as temperature decreasing，leaves appear gradually water-soaked spots， chlorosis until withered and abscission， in which， damage symptom of D． sapidus leaf is the most serious． Under natural low temperature conditions， chlorophyll content in leaf of three species appears decreasing trend generally， relative electric conductivity increases gradually with decreasing of daily minimum temperature， while MDA content and SOD activity appear the fluctuation tendency． Compared with daily minimum temperature of 15 ℃ ， decreasing range of chlorophyll content and SOD activity in leaf of D． sapidu is the greatest but that of D． minor var．amoenus is the least， and relative electric conductivity of D． sapidus is the highest while that of D． minor var． amoenus is the lowest under daily minimum temperature of －2 ℃ ． According to LT₅₀ and changes of morphological and physiological indexes， it is determined that cold resistance of three bamboo species are all weak， in which， that of D． sapidus is the weakest．