干旱胁迫下大豆与玉米叶片光破坏的防御

随干旱强度的增加，大豆叶片光呼吸速率（Pr）降低的幅度小于Pn，使Pr／Pn比率升高。在轻度及中度干旱下，PSII光化学效率（Fv／Fm）能在暗置后较快地恢复。随干旱强度的增加，叶片光化学猝灭系数下降，非光化学猝死系数升高。干旱使叶片β－胡萝卜素及紫黄质含量下降，而玉米黄质含量（Z）与叶黄素库增加。与大豆相比，玉米在干旱条件下具有较高的Z含量和较大的叶黄素库。

Protection Against Photodamage in Soybean and Maize Leaves Subjected to Soil Drought Stress

Gas exchang, chlornphyllfluorescence and xanthphyll cycle com-Ponents in leaves of soybean (opinsmax) and maize (Zea may ) under soildmugh stress were measured- Both netPhotosynthehc rate (Pn) and photorespi-ratory rate (Pr) decaxd in response todidught shess. Since the taluction of Prwas much sInaller than that of Pn, the ra-tio of Pr/Pn increased significanily insoybean leaves. A pronounced decline inPhotochendcal efficiency of rs ll (Fv/Fm) was observed during driugh sbess.Evidence is presented tha such a de-crease of Fv/Fm in dicught-sbessed soy-bean and rnaize leaves was associatedwith a shmtilation of the radiationlessdissipation of excitation eneng - The Pho-tochedrical fltiorescence qtIenching de-creased with increasing didugh sbess. Inconthet, the non Phtochendcal fluores-cence quenching increased. A rise in thezeaxanthin content and xanthphyll cyclePool (zeaxanthin antheraxanthin violaxanthin) was observed. CoInndwith the csplan soybean, the oplanrnalze showd a lmper xanthphyll cyclepool and a higher zeaxanhin content un-der didught condihons. The roles of Pho-torespirahon and zeaxanthin-related radi-ationless dissipation of excitation enengin protecting Photosynthetic apparatusfrom PhotodaInag under drigh condi-tion were discussed.