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云杉矮槲寄生(Arceuthobium sichuanense)属半寄生性多年生种子植物,是青海省云杉天然林毁灭性生物灾害之一。本研究首次报道了云杉矮槲寄生在自然条件下可以侵染青杄,并对健康与染病青杄(Picea wilsonii)针叶形态及其光合日变化进行了测定。结果表明:1)染病青杄的针叶长度和宽度显著小于健康青杄(P<0.001),而染病青杄的针叶比叶面积(SLA)显著大于健康青杄(P<0.001);2)云杉矮槲寄生的侵染显著降低了青杄叶片的净光合速率、蒸腾速率以及气孔导度(P<0.05),但不影响其胞间CO2浓度(P=0.32);3)冗余分析(RDA)表明,云杉矮槲寄生的侵染导致青杄对不同环境因子的依赖程度发生变化,健康青杄表现为环境CO2浓度(CO2)>空气温度(Tair)>叶片温度(Tl)>蒸汽压亏缺(Vpd)>空气相对湿度(RH)>光合有效辐射(PAR),而染病青杄则出现Tl>RH>Tair>PAR>Vpd>CO2,且Tl成为影响染病青杄叶片光合与蒸腾作用(Pn、Tr)的主要环境因子,且染病青杄对RH和PAR变化的响应更加敏感。此外,染病青杄叶片的水分利用率(WUE)显著低于健康寄主(P<0.05)。因此,云杉矮槲寄生的侵染可降低青杄对环境的适应能力,从而加速寄主的衰老死亡。
Arceuthobium sichuanense, a semi-parasitic perennial seed plant, is one of the devastating biological disasters of natural spruce forests in Qinghai Province. This study, for the first time, reports that spruce dwarf mistletoe can invade barley in natural conditions and that the coniferous morphology and its photosynthetic diurnal change in healthy and diseased Pieda wilsonii were determined. The results showed that: 1) The length and width of coniferous leaves were significantly less than those of healthy barley (P <0.001), while the specific leaf area (SLA) of infected oak was significantly higher than that of healthy oak (P <0.001); 2 ) The infection of spruce dwarf mistletoe significantly reduced the net photosynthetic rate, transpiration rate and stomatal conductance (P <0.05), but did not affect the intercellular CO2 concentration (P = 0.32). 3) Redundancy Analysis (RDA) showed that the infection of spruce dwarf mistletoe led to the change of the dependence of barley on different environmental factors, and the performance of healthy barley showed as follows: CO2> Tair> Tl, > Vapor pressure (Vpd)> air relative humidity (RH)> photosynthetically active radiation (PAR), while the incidence of barley Tl> RH> Tair> PAR> Vpd> CO2, And transpiration (Pn, Tr) of the major environmental factors, and the infected barley response to changes in RH and PAR more sensitive. In addition, the water use efficiency (WUE) of infected leaves was significantly lower than that of healthy hosts (P <0.05). Therefore, the infection of spruce dwarf mistletoe can reduce the adaptability of barley to the environment, thus accelerating the host’s death from senescence.