研究了西葫芦银叶病发病叶片和叶柄叶绿素代谢特性和叶片叶绿素荧光参数的变化。与对照相比，发病叶片和叶柄叶绿素总量(Chl.a+b)，叶绿素a (Chl.a)，叶绿素b (Chl.b)含量均下降；轻度与重度发病叶片叶绿素a/b增加，中度发病叶片与对照差异不显著，而叶柄比对照降低。西葫芦银叶病对叶片Chl.b的影响比Chl.a大，而对叶柄Chl.a的影响比Chl.b大。发病叶片和叶柄叶绿素酶活性升高，从而使叶绿素降解加速，叶绿素合成中间产物Protoporphyrin IX (Proto IX)，Magnesium protoporphyrin IX (Mg-Proto IX)，Protochlorophyllide (Pchlide)含量降低，Uroporphyrinogen Ⅲ (Uro Ⅲ)含量增加，表明叶绿素合成在 Uro Ⅲ到 Proto Ⅸ受阻。发病叶片最大光化学量子产量(Fv/Fm)，光系统Ⅱ(PSⅡ)的潜在活性(Fv/Fo)，实际光化学效率(φPSⅡ)，光化学淬灭系数(qP)降低，非光化学淬灭系数(NPQ)增加。试验结果表明，西葫芦银叶病破坏了叶绿素合成和降解的动态平衡，叶绿素合成受阻和叶绿素降解加速是导致叶片叶绿素含量降低的原因；发病叶片叶绿体PSⅡ活性受到抑制。
The characteristics of chlorophyll metabolism and change of chlorophyll fluorescence parameters in the silvered leaves and leafstalks of summer squash induced by silverleaf whitefly (SLW) were studied. The content of Chlorophyll a+b (Chl.a+b) 、Chlorophyll a (Chl.a) and Chlorophyll b (Chl.b) in the silvered leaves and leafstalks decreased. The Chl.a/b in the slight and complete silvered leaves was higher than that in the control, but the Chl.a/b in the moderate silvered leaves was not significantly different. The Chl a/b in the leafstalks decreased. Chl.b was affected more seriously in leaves while the Chl.a compacted in the leafstalks. Chlorophylase (chlase) activity significantly increased with the increasing disease grade, so the ratio of chlorophyll degradation increased. Compared with the control treatment, the amount of precursors including Protoporphyrin IX (Proto IX), Magnesium protoporphyrin IX (Mg-Proto IX), Protochlorophyllide (Pchlide) of chlorophyll biosynthesis decreased with the increasing disease grade, while Uroporphyrinogen Ⅲ (Uro Ⅲ) was accumulated in silvered leaves and leafstalks. This suggested that chlorophyll biosynthesis was blocked at the step from Uro Ⅲ to Proto Ⅸ. The maximum efficiency of photosystomⅡ(PSⅡ) Photochemistry ((Fv/Fo)), potentially photochemical activity of PSII Fv/Fo, actual PSⅡefficiency (φPSⅡ), photochemical quenching coefficient (qP) in the silvered leaves decreased, but non-photochemical quenching coefficient (NPQ) in the silvered leaves was reverse. The result showed that summer squash silverleaf disease destroyed the dynamic balance of chlorophyll biosynthesis and degradation. The ratio of chlorophyll biosynthesis decreased and the ratio of chlorophyll degradation increased, so the content of chlorophyll decreased. The change of chlorophyll fluorescence parameters showed that the PSⅡactivity of the silvered leaves was inhibited.