Casuarina equisetifolia is an actinorhizal tree being introduced in agroforestry systems of Pakistan. A study was conducted to observe the seasonal changes in nodular nitrogenase activity (C2H2 reduction) and uptake hydrogenase activity of C. equisetifolia. Nodules showed significant (P SYMBOL 163 f 'Symbol' 0.05) seasonal variation in the nitrogenase and hydrogenase activities which were highest during June (13.52 SYMBOL 109 f 'Symbol' moles C2H4 . g-1 fresh nodule wt. hr-1 and 2.55 SYMBOL 109 f 'Symbol' moles H2 consumed g-1 fresh nodule wt. hr-1, respectively) and lowest during December (0.55 SYMBOL 109 f 'Symbol' moles C2H4 . g-1 fresh nodule wt. hr-1 and 0.23 SYMBOL 109 f 'Symbol' moles H2 consumed g-1 fresh nodule wt. hr-1, respectively). This study has many important and applied ecological implications in the management of horticulture and agroforestry systems of the tropics.
Keyword: Casuarina, Nitrogenase, Hydrogenase, N fixation