92 Current Botany ● Vol 8 ● 2017 INTRODUCTION Wood rotting fungi act as a decomposer and recycler of nutrients in the natural ecosystem. These fungi have been alienated into brown, white, and soft-rot fungi, which are able to grow abundantly on wood which is a rich source of carbon, but deficient in nitrogen source. The growth of these fungi needs perceptive control of their nitrogen economy which is essential for proteinase activity in wood, and for the intracellular restructuring of nitrogen from mycelial protein (Wadekar et al., 1995) Phlebiopsis gigantea (syn. P. gigantea, P. gigantea) belongs to the phylum Basidiomycota is a white rot fungi. It is commonly found on dead wood growing on Indian Himalayas and Bhutan (Prasher, 2015). It is a saprotroph which derives its carbon from already dead cells. It has not been reported as a pathogen on mature woody trees, however, evidence of colonization of non-suberized spruce seedling roots has been demonstrated which suggest that it may occur as a potential facultative pathogen (Pratt et al., 1999; Pratt et al., 2000; Sui et al., 2009). It is capable of forming structures in spruce wood that are similar to the mycorrhizal mantle on the tree roots (Vasiliauskas et al., 2007). It has also been investigated for its immediate colonization of stump wood competitive ability against Heterobasidion annosum and its capability to turn out a large amount of asexual spores in culture (Hacskaylo et al., 1954; Asiegbu et al., 1996; Woodward et al., 1998). In spite of such a large number of morphological attributes of this fungus; which can be exploited commercially; no studies have been conducted for optimizing the growth of P. gigantea with respect to different physical factors such as temperature, pH, days of incubation, and effect of different carbon and nitrogen requirement. MATERIALS AND METHODS P. gigantea was collected from an unidentified fallen angiosperms twig from Bilaspur, Himachal Pradesh (India).The fungus was isolated on malt extract agar which is prepare according to given instructions and then isolated in a sterile condition by single hyphal tip in Petri-plates kept at 24°C.The mycelium was sub cultured on the same medium for further experimentation. Procedure P. gigantea shows a different effect in basal media, temperature, pH, days of incubation, and carbon and nitrogen source in static conditions. The fungus culture was grown in 100 ml Erlenmeyer flasks containing 25 ml of Nutritional characteristics and physiological studies on the growth and development of Phlebiopsis gigantea I. B. Prasher 1 , Sushma Negi 2 *, Rajeev Kumar 2 1 Department of Botany, Mycology and Plant Pathology Laboratory, Panjab University, Chandigarh, India, 2 Department of Environmental Studies, Panjab University, Chandigarh, India ABSTRACT Physiological studies pertaining to the effect of physical factors, carbon and nitrogen requirement of Phlebiopsis gigantea were conducted to know its behavior in vitro. These studies have revealed interesting results regarding its growth and reproduction behavior. The best medium for the optimum growth is glucose-peptone medium. The optimum temperature (28°C) and pH (5.0) is required for the optimum mycelial production of P. gigantea after 12 days of incubation. The fungus shows best growth in D(+) glucose and sodium nitrate whereas least growth is observed in sucrose and ammonium nitrate medium among various carbon and nitrogen sources, respectively, DL-threonine is found to be best among various organic nitrogen compounds for the growth of fungal mycelium. KEY WORDS: Nutritional requirements, Phlebiopsis gigantea, wood rotting fungi Original Article Current Botany 2017, 8: 92-96 http://scienceflora.org/journals/index.php/cb/ doi: 10.19071/cb.2017.v8.3180 Received: 22-02-2017 Accepted: 31-05-2017 Published: 03-06-2017 *Address for correspondence: Sushma Negi, Department of Environmental Studies, Panjab University, Chandigarh, India. Phone:+91-7837452698. E-mail: sushi.negi14@gmail. com