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American Fern Journal 85[2):58-60 (1995) Diurnal Acid Metabolism Submerged in the Aquatic Plant, Isoetes tuberculata Sharma and Harsh B.D. R. Dapartment of Botany, JN Vyas University, Jodlipur, India 342001 metabolism carry out Crassulacean Acid Metabolism (CAM) CAM process, CO^, fixed into malic acid during is enzyme PEP carboxylase enhanced. During le is CO, decarboxylation of fixed enters into the C3 cycle. ime the diurnal acid metabolism Engelm plant, Isoetes howellii kn 1985, 1987; Keeley and Bowes, Keeley 1982; genus et 1983). In India, the al., by Isoetes is represented several species (Gena and Bhardwaja, 1984; Panigra- 1981; Pant and Sharma hi, Srivastava, 1962; and they occur et 1985), as al., amphibious, submerged terrestrial, or aquatic plants. Diurnal acid metabolism time submer in a sim method of monitorin period. Methods and Materials Well-established, submerged plants of tuberculata growing an in artificial /. pond mg were selected. 50 leaf samples were washed with water, distilled dried by pressing on and pH blotting paper, crushed The in distilled water. of the resulting solution was measured with a Toshniwal pH For each meter. was plant, this procedure repeated at 3 hour intervals up 40 hours, with the to arefully pond was measured same artificial also the at Results and Discussion pH The changes in the of leaf contents during hours two days different of and shown pH nights are The in Fig. decreases during and 1. the night increases during the This day. indicates that there an increase in acidification is CAM during the dark, probably due an accumulation to of malic acid. In plants, it is malic acid that increases during the night. This malic acid is uti- pH during and lized the day, the thus increases then. dH During the same neriod of time, the of the nnnd watRr alsn c;bnwpd slipht SHARMA & HARSH: DIURNAL ACID METABOLISM ISOETES IN 59 Isoetes tuberculata 10 9 PondwQter 8 7 Leaf 6 5 CL /; 3 2 1 1 I 1 1 I 1 10 7 10 16 19 22 7 13 13 1 I, 1 I, HOURS pH day and During the Fig. Changes of in the leaves of Isoetes tuberculata during the night. 1. same period, water from the surrounding pond habitat shows negligible changes. changes during the day and night. However, this variation is negligible (Fig. 1). amounts show of tuberculata significant Preliminary investigations that in /. CAM diurnal acid metabolism occur, and suggest that this species is a plant. pH method However, simple measurement of not a conclusive for deter- is CAM pH may An changes absence of mining the operation of in a species. CAM. than the absence of Titration (Kee- well-buffered cytosol, rather reflect a CAM. more method elucidating Further investiga- 1983) a accurate for ley, is tions in this regard are being undertaken in this laboratory. Literature Cited HARDW B AJ Bombay 81:165-168. Nat. Hist. Soc. 420-424 Keeley, 1981 E. J. submerged aquatic Isoetes hovveUii 1983. Crassulacean acid metabolism in the seasonally . Oecologia 28:57-62. CAM economy submerged aquatic Isoetes howellii The carbon of the 1985. role of in the . Angew. Limnol. 22:2909-2911. Vereinigung Theor. Verb. Int. 1987. The adaptive radiation of photosynthetic modes in the genus Isoetes (Isoetaceae) . and amphibious Black aquatic habitats. 113-128 M. M. Crawford, Plant in Pp. in R. ed., life England. Oxford, well Scientific Publications, submerged aquatic eras and Bowes. 1982. Gas exchange characteristics of the Keeley, G. E., J. 70:1455-1458. Physiol. sulacean acid metabolism plant Isoetes howellii. Pi. AMERICAN 60 FERN JOURNAL Keeley, Mathews, and M. Walker. E., R. P. C. 1983. Diurnal acid metabolism in Isoetes howellii J. from a temporary pool and a permanent Amer. 70:854-857. lake. Bot. J. Kluge, and M., P. Ting. 1978. Crassulacean acid metabolism (CAM): Analysis an I. of ecological adaptation. Springer- Verlag, Berlin. PANIGRAHI. G. 1981. Svstematirs of the Peniis TfinRfR<; fTcnpfarP^ip) in TnHia TnrliaTi n\n] \Aam T. 6:129-138. Pant, and D. D., G. K. Srivastava. 1962. The genus Isoetes in India. Proc. Nat. Inst. Sci. India, Pt. B, Biol. Sci. 28:242-280. Sharma, B. D., R. Singh, and M. S. Vyas. 1985. Isoetes in Rajasthan—a systematic study. Bull. Bot. Surv. India 27:58-62.