低温对日光温室砂糖橘成花诱导及生理反应的影响

Flower induction and physiological response of Citrus reticulata “Shatangju” to low temperature under solar greenhouse condition

为探索日光温室柑橘花芽进行形态分化的适宜升温时期,以4年生枳砧砂糖橘幼树为试验材料,采用离体培养方法,研究日光温室砂糖橘对低温诱导的成花响应。结果表明：15℃/10℃（昼12 h/夜12 h）低温处理720 h,便能诱导砂糖橘离体茎段腋芽成花,处理960 h后砂糖橘离体茎段腋芽成花率呈下降趋势,而萌芽率急剧上升,成花率与萌芽率呈负相关。日光温室砂糖橘秋梢11月初开始形成花芽,整个冬季秋梢成花率呈升高趋势,平均成花率表现为2月〉1月〉12月。5~20℃低温累计小时数达到1 309 h后,成花率趋于稳定,达到40.51%。有叶花/无叶花比值与〈5℃低温累计小时数呈极显著负相关。砂糖橘成花率与枝条C/N呈正相关,与脯氨酸含量呈极显著正相关。砂糖橘枝条C/N和脯氨酸含量的变化对低温诱导砂糖橘成花表现出一种积极响应。因此,在确定花芽萌发升温时间时,枝条C/N和脯氨酸含量变化可以作为判定指标。

Open-field cultivation has been the main mode of citrus cultivation in China,with major blooming peak in spring and citrus fruits only shipped to markets in October through December.Under protected cultivation,it was possible to force the flowering stage of citrus to an advanced date via temperature control for earlier shipments of fruits to markets.In north China,early autumn low temperatures in solar greenhouses have been used to induce early citrus flower bud differentiation.Induction of flowers by the warming effect with plastic film covers forced sprouting.While the role of the low temperature in flowering has been well documented,flower bud differentiation competence during winter under greenhouse conditions has remained unconfirmed.To determine suitable heating time for citrus flower bud morphological differentiation in solar greenhouse,4-year-old of ＂Shatangju＂ tangerine（Citrus reticulata ＂Shatangju＂） seedlings with stock of trifoliate orange（Poncirus trifoliate Raf.） were selected.The response of the ＂Shatangju＂ tangerine flower to low temperature in solar greenhouse was studied in an in vitro culture.The results showed that some axillary buds differentiated into flower buds after treated with low temperature（15 ℃ at day for 12 h,10 ℃ at night for 12 h） for 720 hours.Floral ratio apparently decreased while germination ratio sharply increased after 960 hours under low temperature.Floral ratio was negatively correlated with germination ratio.Under solar greenhouse conditions,autumn shoots of ＂Shatangju＂ tangerine were ripe enough to form flower buds in early November.Floral ratio apparently increased during the whole of winter,which showed order of average floral ratio： February ＆gt; January ＆gt; December.When accumulated time of low temperature 5~20 ℃ reached 1 309 hours,floral ratio stabilized at 40.51%.A significantly negative correlation was noted between leafy to leafless flower ratio and accumulated hours of ＆lt;5 ℃.Under low temperature treatment,C/N ratio was positively correlated with floral ratio while proline content showed a highly significant positive correlation with floral ratio.The response of the change in C/N ratio and proline content of ＂Shatangju＂ tangerine was positive to flower induction.In conclusion,change in C/N ratio and shoot proline content were good indicators for heat treatment of citrus to force flower bud germination.