温州蜜柑叶片气体交换和叶绿素荧光对低温的响应

Responses of Gas Exchange and Chlorophyll Fluorescence to Different Low Temperatures in Satsuma Mandarin( Citrus unshiu Marc.)

研究了低温对温州蜜柑叶片气体交换和叶绿素荧光的影响 ,结果表明 :(1) 8℃低温处理 18h对气体交换和叶绿素荧光影响不大。 (2 ) 2℃低温处理 15h后 ,净光合速率 (Pn)、气孔导度 (Gs)、羧化效率 (CE)下降 ,胞间CO2 浓度 (Ci)升高 ,表观量子效率 (AQY)和叶绿素荧光参数F0 及Fv/Fm没有显著变化。 (3)室外自然低温处理 2和 7d ,Pn、Gs、CE、饱和CO2 光合速率、AQY及Fv/Fm显著下降 ,Ci及F0 显著升高 ;在 2 0℃室内 ,Fv/Fm、F0 和AQY比CE和Pn恢复快。 (4 )低温胁迫使Jf(依据叶绿素荧光参数计算所得的电子传递速率 )和Jc(依据CO2 同化测定所得的电子传递速率 )下降 ,Jf/Jc 值升高。 (5 )低温处理降低了Pn和光呼吸速率 (Pr) 。

Changes in gas exchange and chlorophyll fluorescence of Satsuma mandarin ( Citrus unshiu Marc.) leaves following low temperature treatments of potted plants were studied. The results are as follows: (1) After chilling at 8℃ for 18 h, no significant changes in gas exchange and chlorophyll fluorescence were observed (Fig.1A, Table 1). (2) Following 2℃ chilling treatment for 15 h, net photosynthetic rate (Pn), stomatal conductance (Gs), carboxylation efficiency (CE) declined, while intercellular CO 2 concentration (Ci) increased. Apparent photosynthetic quantum yield (AQY) and chlorophyll fluorescence parameters F 0 and Fv/Fm remained essentially unchanged. The recovery of the altered parameters at 20℃ was nearly completed in 1 d (Figs.1B,2A, Table 1). (3) After exposure to outdoor winter low temperatures for 2 d (max.14.5℃, min. -3.5℃, total time below 0℃ was 30 h), Pn, Gs, CE, light saturated and CO 2 saturated photosynthetic rate and AQY as well as Fv/Fm declined, whereas Ci and F 0 increased. With subsequent transfer to the 20℃ [HJ6”:2]culture room, Fv/Fm, F 0, and AQY returned to their initial values in 2 d, but the restoration of CE, and Pn needed about 3 d (Figs.1C,2B, Table 1). Exposure to the outdoor winter low temperatures for 7 d (max.14.5℃, min. -4.0℃ , and total time of 72 h below 0℃) induced more marked changes in these parameters. The altered chlorophyll fluorescence parameters only partly recovered after incubation in the 20℃ room for 2 d, but CE and Pn basically recovered in 5 d (Figs.1D,2C, Table 1). (4) After the plants were exposed to low temperatures, J f (electron transport rate calculated from chlorophyll fluorescence parameters) declined, whereas the ratio of J f/J c (J c represents electron transport rate estimated by CO 2 assimilation measurements) increased with an increase in chilling stress (Table 1). (5) Both net photosynthetic rate (Pn) and photorespiratory rate (Pr) decreased in response to chilling treatment, with the latter to a lesser extant (Fig.3).