O3胁迫对冬小麦籽粒果皮光合能力及灌浆的影响

为揭示高浓度O3对冬小麦籽粒发育和干物质累积的影响,通过OTC设置了活性碳过滤空气(CF,4—28 n L/L)、不通风(5H,15—68 n L/L)、环境空气(NF,7—78 n L/L)、100n L/L O3(CF100,96—108 n L/L)和150n L/L O3(CF150,145—160n L/L)等5种O3熏蒸处理,测量了籽粒干物质累积、光合色素含量及果皮的叶绿素荧光特性(IMAGING-PAM)。结果显示,CF100和CF150处理显著降低了冬小麦籽粒的长度、最大宽度、最大厚度、10粒体积、穗粒数、灌浆持续时间和灌浆高峰结束前的平均灌浆速率,其千粒重在整个灌浆过程中均显著低于NF,收获时分别下降了10.7%和17.8%;CF100和CF150的光合色素含量在扬花后8—16d内显著高于其余3组(伴随着较强的光合能力),扬花16d后迅速下降18d后差异达到显著水平。穗粒重下降的主要原因是籽粒体积缩小、灌浆持续时间缩短和穗粒数下降;高浓度O3在灌浆前期延缓了冬小麦的生育进度,在灌浆后期使得植株迅速衰老,灌浆持续时间大幅缩短;籽粒果皮的最大光合能力在灌浆初期受到一定抑制,在灌浆中期表现出较好的适应性,在中后期由于籽粒衰老提前而迅速下降。高浓度O3条件下,果皮绿色层在籽粒干物质累积和营养物合成过程中发挥着更加重要的作用。

Effects of long-term ozone exposure on the photosynthesis capacity of grain pericarp and grain-filling of winter-wheat

Dry matter accumulation, photosynthetic pigments content and chlorophyll a fluorescence parameters (via IMAGIN-PAM, H. Walz, Effeltrich, Germany) in the pericarp were studied in developing wheat grains in response to varying ozone concentration: charcoal filtered air (CF, O₃ ranging over 4-28 nL/L), ambient air (NF, O₃ ranging over 7-78 nL/L), 100 nL/L O₃ (CF100, O₃ ranging over 96-108 nL/L) and 150 nL/L O₃ (CF150, O₃ ranging over 145-160nL/L) and beside, a closed Open Top Chamber(5H, O₃ ranging over 15-68 nL/L) was set up for comparison. It was observed that CF100 and CF150 treatment significantly reduced the length of winter wheat grain along with its maximum width, maximum thickness, volume, number of grain per ear, grain filling duration and the average filling rate before the end of peak compared with NF. Their 1000-grain weight of CF100 and CF150 was constantly lower than NF (and CF), finally, there was 10.7% and 17.8% decline, respectively. From 8^th to 16^th day after anthesis, CF100 and CF150 were significantly higher than other three groups, yet after 16 days, they declined rapidly to the extent that they lag the other groups significantly after 18^th day. Under enhanced O₃, grain yield decrease resulted mainly from the declining of volume, grain filling duration and number of grain per ear. In conclusion, high concentration of O₃ delayed the grain development process at the earlier period of grain filling but advances senescence at the later period which sharply shorted the grain filling duration. The potential electron transport rate, equivalent to the parameter ETR_max, was suppressed at the beginning of grain filling stage but promoted in middle stage. And then it fell rapidly due to the grain aging in advance. In addition, under high concentration of O₃, the green layer of pericarp played a more important role in dry matter accumulation and nutrient synthesis.