甘蔗幼叶原生质体分离过程中呼吸的变化及其影响因素

Change of Respiration of Young Sugarcane Leaf Tissue During Protoplasts Isolation and Some Factors influencing Them

甘蔗幼叶呼吸途径以ＥＭＰ－ＴＣＡＣ为主，ＰＰＰ活力不强；游离原生质体ＥＭＰ活力与幼叶组织相近，但ＴＣＡＣ活力略有下降，ＰＰＰ活力明显提高，约为幼叶组织的两倍。甘蔗幼叶原生质体在用酶法分离过程中，其组织呼吸速率开始时呈现短暂跃升后即迅速下降。导致呼吸下降的主因是细胞壁降解产物中的某些物质，它们通过钝化呼吸途径中某些关键酶的活性而降低了呼吸活力。

Following a transient rise at theearly stage, the respiratory rate of thetissues from young sugarcane leaf declined quickly during the enzymaticisolation of protoplasts. In the presenceof the mixture of cell wall degradingenzymes, the respiratory rate of theyoung leaf tissues decreased with an increase of the concentration of mannitolused as osmoticum (Fig. 1 ), but to alesser extent in the absence of the cellwall degrading enzymes (Fig. 2 ), Therespiratory rate decreased with an increase of cellulase concentration whenthe concentrations of pectinase andmannitol were kept constant in themixture (Fig. 3 ). As compared withthe pectinase,the harmful effect of cellulase on the respiration of young sugarcane tissues is more POwerful (Fig.4 ).The respiration of freshly prepared protoplasts from young sugarcane leaf was inactivated by the cellwall degradation products (CWDP ),water-extract of cell wall, active anddenatural by boil cell wall degradingenzyme mixture (Fig. 6 ), and thestrongest inactivation was produced byCWDP which inactivated the activitiesof the key respiratory enzymes (Table3),suggesting that the decrease of respiratory activity might be caused mainly by the toxicity of CWDP during theenzymatic isolation of protoplasts.The dominant respiratory pathway was the EMP-TCAC while thepentose phosphate pathway (PPP) activity was relatively weak in the youngleaf of sugarcane. The activity of EMPin the freshly prepared protoplasts wassimilar to that in the intact tissue, butthe TCAC activity was much weaker,whereas the PPP activity was almosttwice as strong as that in the intact tissues (Tables 1 and 2).