混播下柳枝稷叶绿素荧光参数及对水氮条件的响应特征

Fluorescence Kinetic Characteristics of Switchgrass in Mixture under Different Soil Water and Nitrogen Conditions

采用盆栽试验,按照白羊草（Bothriochloa ischaemum）与柳枝稷（Panicum virgatum）株数比设置5个混播比例（0∶8、2∶6、4∶4、6∶2、8∶0）,在两种氮肥处理（不施氮和0.1g N·kg-1）下,测定分析柳枝稷叶绿素荧光参数对土壤水分短期自然干旱并复水[土壤含水量从80%FC（田间持水量为20%）逐渐降至20%FC后再复水至80%FC]的响应,以期揭示不同水氮及混播比例下柳枝稷与白羊草竞争关系的生理生态机制。结果显示：（1）随干旱胁迫加剧,柳枝稷最大光化学效率（Fv/Fm）、光化学猝灭（qP）、实际光化学效率（ΦPSⅡ）和表观光合量子传递速率（ETR）逐渐下降,复水后第2天各指标均可恢复到对照水平;（2）两氮肥处理下,单播柳枝稷的ETR显著高于混播,施氮处理下单播的qP显著高于混播,但非光化学猝灭系数（NPQ）相反（P〈0.05）,且柳枝稷比例越小各指标降幅越大,表明混播后柳枝稷PSⅡ反应中心活性下降,显示出其对混播竞争的适应;（3）施氮显著提高了柳枝稷的ΦPSⅡ（13.64%~23.53%）和qP（6.12%~11.11%）,降低了NPQ值（9.76%~12.82%）（P〈0.05）,表明施氮可提高其光能利用能力,增强其与白羊草的竞争力。研究认为,不同水氮条件下,柳枝稷表现出较强的混播竞争适应性,施氮会提高其对白羊草的生态竞争能力。

To clarify the physiological characteristics of switchgrass as an introduced species in semiarid re- gion, we investigated its leaf fluorescence characteristics when mixed with old world bluestem at five den- sities （i. e. 0 ： 8, 2 ： 6, 4 ： 4, 6 ： 2,8 ： 0） under short-term water stress [soil moisture contents declined from 80% to 20% FC （field capacity is 80%） and then rehydrate to 80% FC]and two nitrogen treatments （No and 0. lg N · kg-1 addition） in a pot experiment. Results showed that. （1） The maximal photochemi- cal efficiency （Fv/Fm）, PS II actual quantum yield （φSps. ）, apparent electron transport rate （ETR） and photochemical quenching coefficient （qP） of switchgrass decreased gradually with soil water drying, and recovered to the same level as with the control plants in the second day after re-watering. （2） ETR value of switchgrass was significantly higher in monocuhure under both N fertilizer treatments, and qP value was significantly higher in monocuhure than those in mixture under nitrogen addition treatment, and vise versa for non-photochemical quenching coefficient（NPQ） value, indicating that the activity of PS Ⅱ reac- tion declined in mixture, and switchgrass had higher competition ability under mixture. （3） ~psu and qP values of switchgrass increased 13.64G--23.53% and 6.12%--11.11%, respectively, and NPQ value de- creased 9.76%--12.82% under N addition treatment, which indicated that N could improve the light ener- gy use efficiency and competitive ability of switchgrass. Our results suggested that switchgrass have strong adaptation when mixed with old world bluestem under different soil water and N application treatments, and N addition could increase its competitive ability to the comtmnent species.