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Two morphological variants of Terminalia alata (Combretaceae) differed in leaf flushing phenology and spatial distribution in a Cambodian deciduous forest. The hairy-type trees displayed leaf exchange behavior in the middle of the dry season. The glabrous type flushed new leaves 3 months after the wet season started. The leafless period of the hairy type was estimated to be

We measured the sap flux densities of 12 deciduous trees in a tropical dry deciduous forest with high seasonality of available water located in Cambodia and evaluated the seasonal trends in transpiration and leaf phenology. For all trees, the minimum transpiration was recorded in the middle of the dry season, and almost all trees restarted transpiration before the first monsoon rain. The occurrence of the ‘paradox’ of leaf phenology was confirmed. During the dry season, transpiration was controlled by leaf phenology and decreased with an increase in the duration of the leafless period. In contrast, during the wet season, daily changes in transpiration were determined by changes in evaporative demand. Transpiration during the dry season accounted for more than 30% of the annual total among trees, and at the stand scale, the dry season contribution was 38%. The dry season transpiration was not negligible for the water balance in this ecosystem. The soil water condition in the shallow layer, where the main root system is located, was not the source of transpiration during the dry season. This implied that the root probably extended to a deep layer and absorbed water. The relationships between the mean canopy stomatal conductance and vapour pressure deficit revealed that most trees were isohydric. Isohydric behaviour controlling stomatal openness to avoid xylem hydraulic failure was also confirmed at the stand scale and was advantageous for these trees, allowing them to continue transpiring under the high evaporative demand during the dry season. Copyright © 2015 John Wiley & Sons, Ltd.

Tipping-bucket flow meter and rain gauge (TBFM/TBRG) are widely used for the measurement of gross rainfall (GR), throughfall (TF), and stemflow (SF) to evaluate the amount of interception loss (I). However, TBFM/TBRG cannot measure the inflow rate during tipping and underestimates the inflow rate. To correct this systematic bias, 33 total calibrations were conducted for five types of TBFM/TBRG in the laboratory. The tipping time increased with the bucket volume, and the underestimation during one tip was higher for TBFM/TBRG of larger capacity. With the use of the scaled actual inflow rate and the actual volume of a single tip from the measured static volume of a single tip when the inflow rate is zero, the common calibration curves were obtained as quadratic equations for each of the five types within an error range of ±3%. We measured GR and TF by using TBRG and TBFM with a resolution of 0.2 mm and measured SF by TBRG with a single-tip static volume of 15.7 cm3 in a Japanese temperate coniferous forest (TCF) and a Cambodian tropical deciduous forest (TDF). At both sites, the calibration curves needed to be applied to obtain GR, TF, and SF on an event scale with an underestimation degree of less than 3%. Without applying any calibrations, the higher rainfall intensities in TDF caused larger underestimations of GR, TF, and SF and larger overestimations of I compared with results for TCF. On an annual scale, the degree of overestimation of I relative to GR (ΔI/GR) was 1.2% in TCF and 3.5% in TDF, and ΔI/I was at least 10% at both sites. Copyright © 2012 John Wiley & Sons, Ltd.

In this study, we measured evapotranspiration in an evergreen broadleaf forest watershed in the Kampong Thom Province of central Cambodia with the aid of a 60-m high meteorological observation tower. The main vegetation species at the study site were Myristica iners and Vatica odorata. The mean tree height in the upper crown layer at the study site was 27·2 m, and the maximum tree height was 45·1 m. A heat balance method, which incorporated the Bowen ratio, was used to calculate the energy balance above the forest canopy; this value was subsequently used for the calculation of evapotranspiration. All the equipment necessary for the measurement of meteorological variables was installed in the observation tower. Data were collected during two distinct sampling periods: October 2003, in the late rainy season, and March 2004, in the middle of the dry season. Daily variations in evapotranspiration were strongly correlated with the measured amount of net radiation above the canopy layer. On the basis of our measurements, the mean evapotranspiration levels of the forest watershed during the late rainy season and the middle of the dry season were 4·3 and 4·6 mm/day, respectively. No significant differences in soil moisture were observed between the middle of the dry season and the late rainy season, probably due to the shallow depth of the water table. The results of this study suggest that the high levels of evapotranspiration recorded during the middle of the dry season reflect the presence of sufficient soil moisture (derived from the shallow water table) and a high vapour-pressure deficit. Copyright © 2008 John Wiley & Sons, Ltd.

Overproduction of flowers increases the attractiveness of a plant to pollinators, but results in increased geitonogamy. In general, flower abscission has been considered to be an event subsequent to the overproduction of flowers. We observed pollinator behavior in Tilia, a self-incompatible, insect-pollinated tree. We found that pollinators sequentially visited inflorescences within a tree; however, when they met with flower abortion by abscission, they were apt to move long distances and leave the tree. We propose that plants may utilize flower abscission as a method for regulating the movements of pollinators by disturbing them in order to prevent geitonogamy.

The sex expression of Tilia japonica is functional andromonoecy (an andromonoecious system with abortion of perfect flowers). Some of protandrous flowers are aborted after shedding pollen grains and thus are functionally male flowers (FMF). When both male and female organs are retained in a flower, the plants can more flexibly regulate sex allocation, or resource allocation to male and female functions than true andromonoecious plants, which is considered as an adaptive significance of functional andromonoecy. However, the plants have to pay some costs of female organ in FMF. For functional andromonoecious plants, there is a conflict between flexibility and cost in determining the timing of flower abortion, or arrest investing in female functions in a flower. We clarified that (i) differentiation of the timing of flower abortion caused two types of FMF: short-style (SS) and normal-style (NS) flowers; (ii) SS can be produced at a lower cost than NS, and (iii) plants having NS can flexibly regulate sex allocation following a sudden change in conditions. Hence, we concluded that differentiation of the timing of flower abortion makes a compromise of the conflict. We also found that NS is more frequent than SS, and we discuss the adaptive significance of keeping potential fertility.

Tilia japonica Simonkai has morphologically perfect flowers with stamens and a pistil. However, some flowers fall without developing into immature fruits. We clarified that: (i) the flower abscission is a facultative abortion, (an abscission layer was observed at the base of the stalk of aborted flowers); (ii) fallen flowers have functional stamens (the flowers are protandrous and they had shed germinable pollen grains before the flower abscission); and (iii) fallen flowers have a non-functional pistil (they were abscised before stigma opening). The aborted flowers were functional male flowers, although they were morphologically perfect. Hence, the functional sex expression of T. japonica is andromonoecous having both perfect and male flowers within an individual tree.

Summary OBJECTIVE The thyroid gland is physiologically stimulated in normal early pregnancy. However, clinical thyrotoxicosis in normal pregnancy has not been well described. In order to clarify this we examined thyroid function and thyrotoxic symptoms in relation to emesis in normal pregnancy. We also investigated the possible mechanism of gestational thyrotoxicosis. DESIGN Thyroid function was evaluated in view of the clinical thyrotoxic symptoms and the severity of gestational emesis in early pregnancy of 51 normal women. Two pregnant women who showed clinical thyrotoxicosis were followed serially during and after pregnancy. MEASUREMENTS Serum free T4, free T3 and TSH were measured by radioimmunoassay and hCG by fluoroimmunoassay. Thyroid-stimulating activity of pregnancy sera was measured by cAMP increase in cultured FRTL-5 cells. RESULTS Fifty-one pregnant women were divided into three groups: those without emesis (n= 24), with emesis (n= 19) and with hyperemesis (n= 8). Serum free T4 and free T3 were higher in the hyperemesis group (P