Table 1.
Energy requirement for malate transport across tonoplast in Kalanchoë pinnata and K. daigremontiana leaves and in pineapple chlorenchyma in the dark
| Pineapple |
K. pinnata |
K. daigremontiana |
||||
|---|---|---|---|---|---|---|
| Ratio of tonoplast PPase activity to ATPase activity | 0·45 : 1 | 1·22 : 1 | 1·42 : 1 | |||
| Ratio of potential transport activity of tonoplast PPase to ATPase | 0·225 : 1 | 0·61 : 1 | 0·71 : 1 | |||
| Net energy requirement for 1 mol malate transport across tonoplast was as follows: | ||||||
| Pineapple: 0·816 ATP + 0·368 PPi → 0·817 ADP + 1·552 Pi; | ||||||
| K. pinnata: 0·621 ATP + 0·758 PPi → 0·621 ADP + 2·137 Pi; | ||||||
| K. daigremontiana: 0·585 ATP + 0·830 PPi → 0·585 ADP + 2·245 Pi. | ||||||
The stoichiometry of H+ : PPi and H+ : ATP is 1 and 2, respectively. The stoichometry of malate2− : H+ is 2 (Lüttge, 1988; Chen et al., 2002).
Data of tonoplast PPase and ATPase activities are taken from Chen and Nose (2000, 2002).