Under phosphate deficiency stress, the mRNA levels of PLDalpha and PLDbeta in tobacco older leaves were higher while in rapid developing ones were lower than those in controls. In addition, changes in PG hydrolase activity were positively correlated with the alternation of transcript levels of PLDalpha and PLDbeta genes in both types of leaves. Phosphate deficiency resulted in decreases in PG content in both older and rapid developing leaves, and that the extent of decrease in older leaves was much larger than that in rapid developing ones. Phosphatidic acid (PA) is one of the main hydrolysis product of PG. Its production was restricted by adding n-butanol, an inhibitor of PA formation via PLD pathway, to the in vitro enzyme reaction mixture. These results suggest that the enhanced PG hydrolase activity is one important cause of the decrease in PG content in older leaves, and the activity of PG hydrolase is regulated at the transcriptional level.