DROUGHT STRESS IN SEEDLINGS - LIPID-METABOLISM AND LIPID-PEROXIDATIONDURING RECOVERY FROM DROUGHT IN LOTUS-CORNICULATUS AND CERASTIUM-FONTANUM

Seedling survival of drought during the first days following germinati on can be one of the most critical factors in successful establishment of the species. Seventy-two hour old seedlings of Cerastium fontanum Baumg. and Lotus corniculatus L. were exposed to severe desiccation fo r 36 h and the recovery of the whole plants monitored over the subsequ ent 17 days. The analysis exposed the very different responses to wate r stress in the two species. The effects of water stress on the less d rought tolerant L. corniculatus within the first 5 to 10 days after dr ought treatment included a 2-fold larger loss in dry weight than in C. fontanum and a 2-fold rise in lipid peroxidation (thiobarbituric acid -reactive substances), in triacylglycerols and in free fatty acids. Th e ratio of monogalactosyl diacylglycerols/digalactosyl diacylglycerols (MGDG/DGDG) declined 3-fold, while the proportion of MGDG was some 12 -fold lower. In contrast, in the relatively drought-tolerant seedlings of C. fontanum no changes of this order were recorded in the days imm ediately following rehydration. The relationship between these changes in lipid metabolism, lipid peroxidation and drought induced damage in terms of growth is discussed in the context of seedling recovery and survival in the two species.