Reduced phosphorus requirement of azolla mexicana native to Egypt

Growth rate of the water fern, Azolla mcxicana [native to Egypt] was examined in different growth media. The medium recommended by the International Rice Research Institute [IRRI] was the best for its multiplication. Azolla mexicana grown on floodwater alone or supplemented with both micro-and macro-nutrients, doubled its weight in about 7 and 3 days respectively. Phosphorus was the main limiting factor for growth and acetylene reduction activity [ARA] when grown on floodwater. Growth and ARA of A. mexicana were also examined under different light intensities and different levels of exogenously added P to the growth medium. Although light intensity about 2 Kix could not produce much biomass, the growth obtained under 20 Klx was approximately the same as that under 40 Klx. Growth of Azolla at 20 ppm phosphorus [P 1] in the medium was similar to that obtained with half this amount [P1/2]. However, ARA was greater at the P 1 level than at the P 1/2 level. This strain of Azolla mexicana appears to be able to withstand light intensity as high as 40 Klx with a reduction in the P requirement, and it may be, therefore, suitable for agronomical use in temperate regions

Influence of ammonium ions on the activity of nitrate reductase in the fresh water fern, azole Carolinian

The effect of NH[4]Cl either as a sole nitrogen source or together with NO[3], on nitrate reductase activity [NR] of the water fern, Azolla caroliniana was studied. Ammonium ions induced slightly the NR activity until 1.0 mM, then the activity decreased. When NH[+4]was added to the induction medium [2/5 N[2-]free Hoagland solution plus 5.0 mM N0[3]] a marked decrease in NR activity was -recorded. Nitrate uptake, assimilation and NR activity of Azolla plants pretreated with 1.0 mM NH[4]for 0,1,2,3 or 4 days were also studied. The uptake of NO[-3]was roughly the same, while NO[3]assimilation was greatly suppressed and, accordingly, accumulation of NO[3]was markedly increased. Maximum NR activity was shown with the non-treated Azolla plants. Ammonium uptake and NTR activity of previously induced or non-induced plants were also investigated. Induced Azolla plant showed a gradual increase in NH[-4]uptake and a marked decrease in NR activity throughout the whole experimental period. However, the non-induced plants absorbed much greater amounts of ammonia than did the induced ones

On the occurrence of the water fern azole mexicana in Egypt

A species of Azolla has recently been detected in an irrigation canal in Gharbiya governerate, Egypt. The first record of Azolla colonies in this canal was in summer 1990. The sample collected was dichotomously branched, 1.5 cm in diameter. Megaspores were pitted and each was provided with three floats. Each microsporocarp contains about 4 massulae covered with anchor-shaped multiseptate glochidia. SEM examination of the leaf like structures revealed the presence of tricellular trichomes. The collected species was, identified as Azolla mexicana