J. Plant Res. 108: 511-515, 1995 Journal of Plant Research ~) by The Botanical Society of Japan 1995 Morphological and Phenological Characteristics of Leaf Development of Durio zibethinus Murray (Bombacaceae) Kazuharu Ogawa', Akio Furukawa 2, Akio Hagihara', Ahmad Makmom Abdullah 3 and Muhamad Awang 3 1 Section of Forest Ecophysiology, School of Agricultural Sciences, Nagoya University, Nagoya, 464-01 Japan 2 Environmental Biology Division, The National Institute for Environmental Studies, Ibaraki, 305 Japan 3 Department of Environmental Sciences, Universiti Pertanian Malaysia, 43400 UPM Serdang, Malaysia The morphological and phenological characteristics of leaf development of Durio zibethinus Murray were inves- tigated at an experimental field of Universiti Pertanian Malaysia (UPM) in Selangor. Proportionality was obser- ved in the relations of leaf length to leaf width and of leaf area to the product of leaf width and length. The propor- tionality was explained from the similarity of leaf shape. New leaves emerged continuously, but the number of new leaves fluctuated seasonally. The emergence of leaves was inhibited by the flower bud formation, in the survival curves of leaves, the relative fall rate was lower at the early stage of leaf development than at the late stage. Leaf longevity of 100 to 133 days was low and leaf expansion period of two weeks was short in compari- son with the published data on tropical trees. From the ecophysiological viewpoint, the leaf survival strategy of the present species was discussed: the present species manages to set up a photosynthetic system in a short period by the rapid leaf growth; the lower leaf longevity is advantageous to reaching more frequently high photosynthetic production by newly emerged leaves. Key words: Bombacaceae -- Durio zibethinus ~ Leaf development-- Relative fall rate -- Survival curve -- Sur- vival strategy Leaves have their own life histories during the period of birth to death due to senescence or some environmental hazard (Harper 1977). These leaves, which are different in age and size, form the crown of a tree. The phenological clarification of their life histories or their developmental processes is helpful for understanding not only the dynamics of crown and canopy, but also the productivity of forests. As reviewed by Kikuzawa (1986), a number of researchers have demonstrated the phenological charac- teristics of leaves of forest trees through an approach of population ecology. Since their studies focused on Correspondence to: K. Ogawa deciduous trees, little is known about evergreen trees. The life styles are phenologically different between decid- uous and evergreen trees. There may exist phenological characteristics specific to the evergreen trees. In the present paper, we deal with a tropical evergreen tree, durian (Durio zibethinus Murray); which is a commer- cially useful species producing fruit as well as an ecologically important species in tropical forests (Idris 1990, Smith et al. 1992). We attempt to analyze the morphological characteristics such as leaf shape and leaf thickness, and the phenological characteristics such as leaf survival and leaf growth. From the ecophysiological viewpoint, the leaf survival strategy is discussed on the basis of the results of phenological characteristics. Materials and Methods Research site This research was conducted on a 23-year-old (as of 1992) cultivated tree of Durio zibethinus Murray at an experimental field station of Universiti Pertanian Malaysia (UPM) in Selangor, Peninsular Malaysia. The tree height, stem diameter at breast height, and long and short branch spreads of the sample tree were 8.8 m, 25.0 cm, and 10.0 and 9.0 m, respectively. The trees were planted in the experimental field distantly enough to be exposed to the full sunlight. Measurement procedures Young and old leaves were sampled five times from August 10 to September 18, 1993. The young and old leaves were distinguished from the appearance of leaves, i.e., light and dark green for young and old leaves, respec- tively. The sampled numbers were totally 40 for young and 62 for old leaves. After sampling, the leaf width (/w) and length (/,) (Fig. 1), dry weight and leaf area were measured. The ranges of/w and/L were 2.20 to 7.32 cm and 6.20 to 17.58 cm in the young leaves, and 2.50 to 7.40 cm and 5.90 to 16.89 cm in the old leaves, respectively. The measurement of leaf area was performed with an area meter (AAC-100, Hayashi, Japan).