Flora (2000) 195, 165-171 http://www.urbanfischer.de/journals/flora ©by Urban & Fischer Verlag Cambial activity and development of wood in Acacia nilotica (L.) DEL. growing in different forests of Gujarat State KisHORE S. RAJPUT and K. S. RAo* * Author for correspondence: Department ofBiosciences, Sardar Patel University, Vallabh Vidyanagar 388120, India Accepted : September 9, 1999 Summary Seasonal activity of cambium was studied in Acacia nilotica (L.) DEL. growing in Moist Deciduous (MDF), Dry Deciduous (DDF) and Scrub land Forests (SF) of Gujarat State for one annual cycle. In MDF cambium was active for major part of the year reaching peak in August. In DDF, cambial cells underwent divisions throughout the year, but recorded maximum in August and September. Cell division and differentiation of cambium in SF occurred in two growth flushes. The first flush of cambial activity began in January, reached peak in April and then declined suddenly in May. The second flush of activity started in October and continued until November. However, cambium remained inactive during monsoon. Seasonal behaviour of vascular cambium has been discussed in relation to local climatic conditions and phenology of the trees. Key words: Seasonal activity, cambium, wood development, Acacia nilotica. Introduction Acacia nilotica (L.) DEL. is a moderate sized spiny ever- green tree indigenous to Sindh, the Deccan, tropical Africa and is naturalised in all parts of India. The bark is a major source of tannin and gum-arabic. Wood is also used in a wide range of artifacts ranging from farming implements, furniture and good quality timber. A few studies have been made on seasonal cambial growth patterns in some species of Acacia (FAHN, 1959, FAHN et al. 1968). IQBAL & GHOUSE (1987) studied structural changes in fusiform cambial cells of Acacia nilotica in relation to age and season. However, no information is available on seasonal behaviour of the vascular cam- bium of Acacia nilotica. Therefore, this paper aims to compare and to understand the response of vascular cambium of Acacia nilotica, a common evergreen tro- pical tree growing in Moist Deciduous, Dry Deciduous and Scrub land Forests. Materials and Methods Samples of cambial tissue along with inner bark and outer sapwood were collected from the main trunk at breast height of 12-15 year old trees of Acacia nilotica 0367-2530/00/195/02-165 $ 12.00/0 (L.) DEL. having similar trunk diameter (35-40 em) which were growing in moist deciduous forest at Wag- hai region of Dangs, dry deciduous forest at Pavagadh and scrubland forest at Nakhatrana. Periodic collections were made from January-December 1994 in the second week of every month. Two trees were sampled each time to obtain four blocks, no tree being sampled more than once. The blocks measuring about 60 x 20 mm were excised with the help of chisel, hammer and single edge blade and fixed in FAA (BERLYN & MIKSCHE 1976). Suitably trimmed small pieces of these blocks were sec- tioned in transverse, radial and tangential longitudinal planes at a thickness of 12-15 f..Lm on a sliding micro- tome. After staining with tannic acid-ferric chloride-lac- moide combination (CHEADLE et al. 1953), the sections were mounted in DPX. The term cambium and cambial zone are used to include the entire population of ray and fusiform cam- bial cells between the xylem and phloem. Cambial activity was determined by counting the number of undifferentiated layers of cambium lying between the xylem and phloem in transverse section. One hundred readings of cambial layers at random were selected to obtain the mean and standard deviation. Seasonal phenological changes of the trees (such as sprouting of foliar buds, full foliage, flowering, fruiting FLORA (2000) 195 165