Culture Studies on Gelidium pusillum (Stackh.) Le Jolis

Gelidium pusillum was grown in media of von Stosch, Chen etal. and Schreiber. Von Stosch's medium was found better for the growth. No spores were producted under any photoperiod. The alga showed two vegetative growth phases. The first one was completed within 3 to 4 months. Increase in fresh weight of the alga was best under 20 hr 4 hr light and dark cycle äs well äs continuous Illumination. During the second growth phase, plants separated into a number of small bushlets, more so in the cultures given 8 hr 6 hr light and dark cycle. Fragments of the alga, äs small äs 2 mm in length, can regenerate without any loss in their capacity to produce proliferations. Plants grown in cultures yielded 22% agar having a gel strength of 210 g/cm. Introduction Gelidium pusillum from Saurashtra coast can be considered äs one of the alternate sources for agar production in India, äs it yields 24% agar having a gel strength of 169 g/cm. However, due to the small size of the plant (2-3 cm long) and its less availability in nature, harvesting of the alga from nature is difficult. The capacity of the alga to proliferate quickly in cultures can be advantageously utilized in growing it in free floating cultures. In the present study, an attempt has been made to find out suitable culture media and a photoperiod required for best growth, normal pigmentation and morphology. Capacity and mode of regeneration of the alga, starting from single individuals and fragments of the thallus were also studied. Materials and Methode Healtliy plants of Gelidium pusillum were obtained from Veraval, and separated into single individuals. Plants were grown in 300 ml of von Stosch (1964), Chen et al. (1969) SMWIII (without liver extract and thymine) and Schreiber media (Provasoli et al 1957)» taken separately in 500 ml round but flat bottomed flasks. Cultures were given 16 hr-li hr light and dark period, with an illumination of 2000 to 2500 lux provided from 40 W daylight cool fluorescent tubes. Temperature of the cultures was 22 ± 2 C. Cultures were frequently aerated and culture media changed every 15 days. Growth was measured by taking fresh weight of the plants after surface moisture was removed by filier paper towellings. Percentage increase in fresh weight of the plants was also calculated. To study the effect of different photoperiods, ten single individuals were grown under 8 hr-16 hr, 16 hr-8 hr and 20 hr—4 hr light and dark cycle äs well äs under continuous illumination, initially in Schreiber's medium (for 2'/2 months) and then in von Stosch's medium (since this medium was found better) upto the end of the experiment. Temperature and illumination remained the same äs in earlier experiments. Every month observations on morphology and pigmentation of the plants and data on the number of proliferations produced per plant, length of the longest proliferation and fresh weight of the plants were taken. Percentage increase in fresh weight of the plants was also calculated. To investigate the possibility of increasing the number of inocula fragments of the thallus were used, besides the single individuals. To investigate suitable size of the fragments to be used for propagation of the plants, healthy single individuals were taken into two batches of equal fresh weight. Plants of one batch, were cut into fragments l to 5 mm in length. In this batch three types of fragments could be distinguished. ( l ) Fragments with apical cell intact and the other end cut. (2) Fragments with both ends cut. (3) Fragments with one end cut, the other end was containing holdfast region. Plants of the other batch were used äs single individuals for Botanica Marina / Vol. XXI / 1978 / Fase. 3 170 Mairh & Rao: Culture of Gelidium pusillum culture. Both the batches were grown separately in von Stosch's medium under 16 hr-8 hr light-dark cycle and temperature äs in earlier experiments. Results In the experiment where different culture media were used, maximum fresh weight of the plants was obtained in von Stosch's medium (Tab. I). Also, increase in fresh weight over initial was found better in von Stosch's medium (387.3%) than in that of Schreiber (229.3%) and Chen et (173.5%). In all these media pigmentation of the plants was more or less normal, however, in Chen et al medium, plants were comparatively deeply pigmented. Also, maximum length and bushyness of the plants were obtained in the medium von Stosch äs compared to those of Chen et al and Schreiber (Fig. l A and B and Fig. 2). Nitrogen available to the plants in von Stosch's medium is only 7.0 mg/1, while in Schreiber's and Chen et al. media it is 16.5 mg/1 and 28.0 mg/1 respectively. When growth of the alga was considered, the increase in fresh Tab. I. Fresh weight of Gelidium pusillum grown in von Stosch ( V ) Schreiber (S) and Chen et al. (C) media. V Days Fresh weight in grams 1 30 60 90 0.109 0.503 0.522 0.529 0.109 0.250 0.297 0.358 0.117 0.226 0.299 0-320 weight of the alga was found inversely proportional to the quantity of Nitrogen available in each medium (Fig. 2). Growth of diatoms was found greater in Chen et al medium than in von Stosch's and Schreiber's media. Gelidium pusillum grown under different photoperiods äs well äs under continuous Illumination reached maximum fresh weight and füll size within 3 to 4 months (Tab. II and Fig. 3). All plants under different photoperiods remained in vegetative phase and no spores were produced. However the alga showed two growth phases. The first phase of the vegetative growth was completed within 3 to 4 months. During this period many new cylindrical proliferations were produced from the holdfast region and from the surface of the thallus giving the plants a bushy appearence. At the end of the first phase of growth, defoliation of the axes sets in. In the second phase, these bushy proliferated axes separated into a number of bushlets. Maximum number of bushlets (296) were produced in cultures under 8 hr—16 hr light-dark cycle (Tab. II, Fig. 4 and Fig. IC, D). These bushlets continued to grow. In these cultures very little growth of diatoms was observed and plants were deeply pigmented. In the plants, maintained under 16 hr—8 hr and 20 hr—4 hr äs well äs under continuous Illumination, shedding of the proliferations were more severe and many of these decayed. Only few bushlets survived. Later these cultures were overgrown by diatoms. In the latter experiments plants maintained under 14 hrhr light dark cycle in von Stosch's medium Tab. II. Number of individuals, theii branches and length of the longest axis and fresh weight of Gelidium pusillum grown under different photoperiods Continuous Illumination Days N L B 20-4 hrs light-dark cycle N L B 16-8 hrs light-dark cycle N L B F 8-16 hrs light-dark cycle N L B F 1