A Model for Estimation of Water Flow Resistance in Soil-Leaf Pathway under Dynamic Conditions

The present study was carried out to establish a model for estimatingwater flow resistance in a soil-leaf pathway under field conditions.In this model, the change in leaf water content is taken intoconsideration; the model is based on the assumption that waterflow resistance is essentially constant for relatively shortperiods. Resistance was estimated for three subtropical woodyspecies growing on shallow-soiled ridges. For the estimation,transpiration rate and leaf water potential were measured directlyin the field, and leaf water content was estimated based onthe relationship between leaf water potential and relative leafwater content as observed in the laboratory. Resistance showedlittle variation with change in leaf water potential and transpirationrate by day but was particularly high in the evening in allspecies. The reason for this is not known but was perhaps dueto inaccurate measurement for transpiration rate. It was consideredto be pertinent to compare daily values of resistance so asto assess plant adaptation to drought. The model was shown tobe useful for estimating resistance from conventional measurementsin the field. Key words: Leaf water content, leaf water potential, transpiration rate, water flow resistance     

Size-Structures and Reproductive Characteristics in Diploid and Triploid Populations of Disporum sessile D. Don (Liliaceae)

Abstract Disporum sessile (Liliaceae), a perennial herb of temperate forests is composed of diploid (2n=16) and triploid (2n=24) populations. The size structure differed remarkably as triploid populations had few small plants and no seedlings. Triploid flowering plants were considerably larger than diploids. Triploids that flowered were 2.5 times larger than diploids that flowered and the size of vegetative ramets produced by triploids was twice as large. In triploids, fruiting rates were quite low only with inviable seeds and vegetative propagule size was greater than that of diploids. As regards growth parameters that help to increase plant size, triploids were superior to diploids. Differences in growth and reproductive parameters between diploids and triploids may contribute to forming different patch sizes.     

Strongly biased sex ratio in cuckoo wasp Chrysura hirsuta (Hymenoptera: Chrysididae), a parasitoid of the mason bee Osmia orientalis

We examined the rate of parasitism and sex ratio of the cuckoo wasp Chrysura hirsuta (Gerstaecker) (Hymenoptera: Chrysididae) that emerged from nests of the mason bee Osmia orientalis Benoist (Hymenoptera: Megachilidae) in Nara, Japan. Nests of O. orientalis were found in empty shells of two snail species, Satsuma japonica (Pfeiffer) and Euhadra amaliae (Kobelt). The percentage of parasitism by cuckoo wasps per all collected cocoons tended to be high (20–50%) even though interannual variation and the average number of cocoons per nest did not differ across snail shell species within each year. Our results from three years of observation, combined with previous reports, showed that the adult sex ratio of C. hirsuta was strongly female‐biased, which suggests that the species reproduces by thelytokous parthenogenesis.