Histological and biochemical changes in Pinus spp. seeds during germination and post germinative growth: triacylglycerol distribution and catalase activity

The spatio-temporal evolution of catalase activity and triacylglycerol distribution were investigated in seeds and seedlings from Pinus pinaster, P. pinea and P. radiata during germination and post-germination. The high amount of triacylglycerols contained in the whole dehydrated embryo from the 3 species, was progressively depleted from the radicle to the cotyledons during the post-germinative growth. The concomitant decrease in area in which the catalase was active occurred in the same tissues, and the quantitative analysis confirmed the involvement of this enzyme in cell detoxification from peroxide released during the intense lipid breakdown. Two isozymes namely CAT-1 and CAT-2 were identified during the post-germinative growth. Both were particularly active in the hypocotyl and radicle while CAT-2 was specifically active in the photosynthetic tissues. These results underlined that catalase activity is also independent from the lipid metabolism in certain territories. The role of each isozyme is discussed in connection with the metabolic changes occurring during seed germination and seedling growth. Special attention is given to the role of the shoot apex in triacylglycerol storage and breakdown