Growth and morphology of Spirodela polyrhiza and S-punctata (Lemnaceae) asaffected by some environmental factors

Effects of pH, light intensity, temperature and shaking on the growth and m orphology of Spirodela polyrhiza Dh116 and S, punctata Dh122 (Lemnaceae) ha ve been studied in the controlled laboratory conditions. pH 6.0 is most sui table for both the speices. S. polyrhiza died at pH 4.0, while in S. puncta ra a very few fronds died. Both the species grew quite well up to pH 9.0. I n both the species, the low pH affected chi a formation and high pH affecte d chi b formation. In general S. punctata had a very high chls: f, wt, rati o than S. polyrhiza. Lower light quantities than 80 mu E m(-2)s(-1) signifi cantly reduced the fresh weight, root length, frond number and thickness of both the species. Surface area was significantly reduced at low light quan tities in S. polyrhiza, our Ir was unaffected In S. punctata. At a light fl ux of 80 mu E m(-2)s(-1) maximum wt. per frond was obtained. Chls : f. wt. ratio of both the species was low at a light flux of 150 mu E m(-2)s(-1) co mpared to that at 80 mu E m(-2)s(-1).S. punctata was severely affected at h igher light intensity. Significantly higher yield and number of fronds were observed in S. polyrhiza Dh116 and S. punctara Dh122 at 33 and 25 degrees C respectively. Shaking at the rate of 55 oscillations min(-1) did not have any effect on the growth of the two species.