强光诱导叶片和盐藻在505nm的差示吸收和叶绿素荧光的变化

HIGH LIGHT-INDUCED CHANGES OF THE DIFFERENTIAL ABSORBANCE AT 505 nm AND CHLOROPHYLL FLUORESCENCE IN LEAVES AND IN GREEN ALGA DUNALIELLA SALINA

摘要:

用分光光度计直接测定几种植物叶圆片和单细胞盐藻照强光（1500μmolm-2s-1）前后在505nm（玉米黄质吸收峰）的光一暗差示吸收变化。短期照光的时问进程中，芦荟（Aloevera）、芒果（Mangiferaindica）、白菜（BrassicaChinensiS）和苦卖菜（SonchusOleraceus）的AA505持续增高，达最大值后有所下降。加入抗坏血酸能刺激光下AA505增大。光诱导的AA505可在暗下消失。单细胞盐藻M50，受光诱导的变化趋势与高等植物叶片相似。研究表明，强光下植物体内出现活跃的与紫黄质去环氧化反应有关的光保护机制的运行，其状况可直接用M505作为检测指标。与白光相比，红色强光只有照射5min时才引·起盐藻AA505上升，在5-90min照光过程中对Fv／Fm的影响比白光小，对AA540的影响比白光大，但两种光反对光合色素的影响没有差异。

Abstract:

The increase of the differential absorbance at 505 nm(△A505) induced by highlight was measured in leaves of Aloe vera, Mangifera indica, Brassica chinensis, Sonchusoleraceus and unicellular green alga Dunaliella salina 1009. Absorbances of leaf discs andalga solution were measured directly by using a spectrophotometer after high light treatment. The differential absorbance was obtained from absorbent difference between thesamples under high light and in the dark. Leaves were collected at 8 a.m. and reservedin the dark to ensure the high content of violaxanthin. During the high lightl 500 μmol m-2S-1) exposure period, △A505, increased gradually in all tested plant species andDunaliella salina. The obvious increase of △505 could be found after short time exposure(5-10 min). The maximum of △A505 was observed during the time of exposure for 50 min depending on the species tested, then it slightly decreased. The presence of ascorbicacid stimulated the light-induced △A505 increment in Aloe leaves and Dunaliella cells. Theincrease of △A505 in illuminated leaves of Aloe and Sonchus disappeared during thesubsequent 5h-recovery in the dark. The result supported that △A505 is an useful and simpleindicator of in vivo violaxanthin de-epoxidation, and the xanthophyll cycle operates activelyin both higher and lower plants under high light condition. Red and white lights at thelevel of 1850 μmol m-2s-1 were chosen to irradiate the sample for comparing their effects on△A505 △A540 (light scattering, an indicator of energy state of chloroplast) as well as pigmentsand chlorophyll fluorescence of Dunaliella salina. These two light sources led to thedecrease of Fv/Fm, Fv/Fo and Fo, showing the characteristics of reversible photoinhibitionduring light exposure from 5 min to 90 min. No difference in pigment content or the ratiobetween chlorophyll and carotenoid was found under the two light sources. However, redlight showed less effect on PS II primary photochemical efficiency and △A505, but moreeffect on energy state as compared with white light.