The seeds of Pinus tahidiformis were cultivated at (25 ± 1 ) ℃ in an incubator and the respiratory rate, activities of PGI, MDH and G-6-PDH and 6-PGDH of the seeds were measured to investigate changes in respiratory intensity and pathways during the initial germinating stages. The results showed that changes in the respiratory rate could be divided into three stages;rapid increase,stagnation and rapid increase again. The rapid increase stage occurred at the first 27 h,and the respiratory rate rose from 0.5 μmol·g-1 min to 12.79μmol·g-1 min . Within the following 18 h, respiratory rate was basically stable ranged from 12.79 to 13.55 μnol·g-1 min-1 . After 45 h incubation, the seed respiratory rate rapidly increased again. When the radicle emerged, the second peak value of respiration was 20.23 μmol og-1min-1. Activities of all respiratory enzymes increased during the initial germinating stages. The PGI activity increased rapidly and reached to the maximal value of 52. 25 OD·g-1 DW in 27 h, and then decreased rapidly. MDH activity did not change obviously in the first 36 h, and afterwards increased to a peak value of 30. 84 U·g-1min-1 in 72 h. The G-6-PDH and 6-PGDH activity increased slowly from 21. 6 U· g-1 min-1 to 29. 04 U ·g-1min-1 in the first 36 h, thereafter, the activity increased rapidly and reached to a peak value of 57. 9 U o g min" with radicle emergence. In conclusion, respiratory metabolism pathways at the early stages of incubation were mainly EMP and PPP, especially EMP pathway. Whereas,during the late stages,EMP, TCA and PPP pathways coexisted,and PPP pathway was predominant.%呼吸代谢是一切生物所共有的生理功能,其重要作用是释放能量供各种代谢的需要.种子萌发过程中糖氧化降解是通过呼吸代谢途径进行的,胚乳中的糖需经氧化分解才能为胚的生长提供可利用的能量,并为新器官、新组织的形成提供重要原料(傅道昭,1980).种子萌发过程不同的呼吸代谢途径为胚的生长提供不同的能荷和还原力,呼吸代谢途径及强度的转变影响种子萌发的正常进行,因此研究种子萌发过程中呼吸代谢具有重要的意义.过去,人们对种子萌发初始阶段,即干燥种子吸水至胚根突破种壳阶段(郑光华,2004)呼吸代谢有一些研究,如水稻( Oryza sativa)、小麦(Triticum aestivum)等种子的顺利萌发是糖酵解途径转变为磷酸戊糖途径,NADH转变为NADPH所致(侯夫云,2005).
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