Tetsuo Sakuratani

A Heat Balance Method for Measuring Water Flux in the Stem of Intact Plants

This paper describes the method and apparatus for measuring the flow rate of water in intact plant stems, on the basis of heat balance of a stem segment. Under stationary conditions, the heat energy supplied continuously to a segment of plant stem is partitioned into three components such as conduction, mass flow and convection [see Eq. (1)]. By predetermining both heat losses due to conduction in the stem and convection from the segment surface into ambient air, it is possible to evaluate the heat loss due to mass flow of water in the stem, that is, the water flow rate equivalent to the transpiration stream. The water flow rate evaluated by this method is compared with the transpiration loss of water determined directly by weighing potted soybean and sunflower plants and measured by using a chamber method. The comparison shows there is a good agreement between them. This indicates that the newly developed method can be applied for determining transpiration rates of intact plants under laboratory and field conditions.

Alterations in photosynthesis and some antioxidant enzymatic activities of mungbean subjected to waterlogging

Abstract Photosynthetic rate ( P ), leaf water potential ( ψ L ) and chlorophyll fluorescence were studied in mungbean plants subjected to waterlogging in a plastic greenhouse, and leaf samples were collected for the analysis of enzymes involved in anti-oxidant photoprotection. Waterlogging caused a fast decline in the photosynthetic rate and water use efficiency without changes of transpiration rate and stomatal conductance during the early waterlogging period, which indicates that reduction of photosynthetic rate might be due to a mechanism independent from stomatal closure. Early reduction of Fv/Fm value of chlorophyll fluorescence by waterlogging indicates that the early reduction of photosynthetic rate is correlated with photo inhibition of photosystem II (PSII). Stomatal conductance and water use efficiency was decreased progressively during prolonged waterlogging while ψ L was unchanged, indicating stomatal closure without water stress. The activities of active oxygen processing enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) decreased during prolonged waterlogging indicating no evidence of oxidative stress and/or damage in leaves of mungbean by waterlogging. Our results suggest that oxidative damage is not directly involved in damage to the photosynthetic machinery during waterlogging in mungbean plants.

High temperature effects on cherimoya fruit set, growth and development under greenhouse conditions

The effects of warm (30/25°C) and cool (20/15°C) day/night temperatures on fruit set and fruit growth of potted cherimoya (Annona cherimola Mill.) trees were investigated under sunlit glass-house conditions. Pollen germination percentage was adversely affected by warm temperatures. Fruit set at warm temperatures was very low, ascribed to both pollen and stigmatic damage from heat stress, although the former was more sensitive to warm temperatures than female organs. Fruit at warm temperatures grew slowly and required more days to mature than those at cool temperatures. Warm temperatures reduced fruit growth rates at the initial and final growth stages. The intervening growth deceleration period was longer at warm temperatures. Warm temperatures produced asymmetrical and small fruit containing a small number of seeds, caused by low-viability pollen. Temperature had no significant effect on the total soluble solid content in fruit.

Growth, flowering and leaf properties of pear cultivars grafted on two Asian pear rootstock seedlings under NaCl irrigation.

The growth responses of grafted young pear trees under salinity were studied. Chinese, Japanese and European pear cultivars (Yari, Kosui and La France) were grafted onto 3-year-old Pyrus betulifolia Bunge (BET) and P. pyrifolia (Burm f.) Nakai (PYR) seedlings. They were grown in pots with sand and irrigated with 20% Hoagland’s plus 0, 25 or 50 mM NaCl solution. All scions grafted onto BET grew well even under 50 mM NaCl irrigation, while those grafted onto PYR suffered from NaCl deficiency heavily. Flower bud formation was stimulated by NaCl treatment in every scion‐rootstock combination. Bloom date and number of flowers per cluster were not affected by NaCl treatment. Mineral analysis suggested that BET’s salt tolerance is due to the ability of this cultivar to restrict Na and Cl ion transport to leaves. # 2000 Elsevier Science B.V. All rights reserved.

Effects of sodium chloride on survival and stem elongation of two Asian pear rootstock seedlings

Survival, leaf burn, and mineral uptake of two Asian Pyrus rootstocks were evaluated under NaCl irrigation. Potted seedlings of 2-year-old pear rootstocks, Pyrus betulifolia Bunge (BET) and P. pyrifolia (Burm f.) Nakai (PYR) were irrigated with 0, 25, 50, 100, 150 or 200 (BET only) mM NaCl solution. BET showed high survival rate and slight leaf injury even under 100 mM NaCl irrigation. PYR however exhibited severe leaf injury and most of the tested plants died under 25 mM NaCl irrigation. Leaf Na concentration in BET subjected to 100 mM was similar to that of PYR at 25 mM.

A split-root apparatus for examining the effects of hydraulic lift by trees on the water status of neighbouring crops

We describe a split-root system for examining the effects of hydraulic lift by trees on crop growth. In this system, upper lateral tree roots were grown in a container set on the ground through which the taproot of the tree could penetrate into the moist soil below. The container, with a radius of 0.5 m and a height of 0.20 m, consisted of two compartments divided by a waterproof barrier. A markhamia tree (Markhamia lutea (Benth.) Schumann) and upland rice (Oryza sativa (L.)) plants were planted in one compartment, with only rice plants planted in the other compartment. Irrigation of the container was ceased at the start of the experiment. The stomatal conductance of the rice plants in the associated side, in which both trees and rice plants were grown, declined more rapidly during the first drying period than in the rice-only compartment, suggesting that there was competition for water between the tree and the crop plants. However, during the later drying period, the rice plants in the associated side were green and viable, while those in the rice-only side became desiccated. Rice roots were seen intermingling with tree roots, and the soil water content in the associated site tended to be higher than in the rice-only side. It is likely that hydraulic lift occurred in the associated side and that water that had been transferred to the surface roots was released into the soil, enabling the rice plants in this compartment to remain viable. This novel system is useful for examination of the effects of hydraulic lift by trees on the growth of neighbouring crops.

Effects of Waterlogging at Vegetative and Reproductive Growth Stages on Photosynthesis, Leaf Water Potential and Yield in Mungbean

Abstract The effects of short-term waterlogging on mungbean and recovery from the damage were studied in a plastic greenhouse. Pot-grown plants of two mungbean cultivars, KPS1 and CNXP-49 were waterlogged for eight days, at the vegetative and reproductive growth stages. Photosynthetic rate (P), transpiration rate (Tr), diffusive resistance (rs) and leaf water potential (Ψl) were measured at the 1st, 4th and 8th day of the 8-day waterlogging treatment and at the 4th and 8th day after the end of waterlogging. P was reduced significantly by waterlogging. It was reduced by 58 and 64% at the 8th day of waterlogging at the vegetative and reproductive stages, respectively, in KPS1 and, by 76 and 82%, respectively, in CNXP-49. Tr was reduced by 48 and 66% in KPS1 and CNXP-49 respectively, at the 8th day of waterlogging at both stages. The diffusive resistance at the 8th day of waterlogging was increased by 79 and 83%, in KPS1 and CNXP-49, respectively, at the vegetative stage, and by 76 and 79% at the reproductive stage. All these physiological parameters of both cultivars recovered to almost normal values within 4 days after the end of waterlogging at the reproductive stage and within 8 days at the vegetative stage. Waterlogging did not affect Ψl, indicating that the decrease in P and Tr was not associated with leaf dehydration. Waterlogging at the vegetative and reproductive stages significantly reduced the dry matter accumulation during and after the waterlogging in both KPS1 and CNXP-49. Final seed yield in KPS1 and CNXP-49 was reduced by 16 and 19%, respectively, by the waterlogging at the vegetative stage and by 23 and 30%, respectively, by that at the reproductive stage. Although even short-term waterlogging markedly affected P, Tr and rs of mungbean, the damage particularly in P and leaf growth was quickly recovered after the end of waterlogging and the reduction of seed yield was less than that expected from the damage in the physiological characteristics. These results, suggest that mungbean has an ability to recover from the short-term waterlogging damage and that the response to waterlogging varies with the cultivar.

Effects of temperature on growth, dry matter production and CO2 assimilation in cherimoya (Annona cherimola Mill.) and sugar apple (Annona squamosa L.) seedlings

Abstract This study compares the growth and physiological response of cherimoya and sugar apple seedlings in order to examine their adaptability to 20/15°C and 30/25°C day/night temperatures in sunlit glass-house conditions. Shoot growth was higher at 30/25°C than at 20/15°C in both species. In sugar apple, temperature had obviously positive effects on shoot growth: the shoot grew vigorously at 30/25°C, but slowly at 20/15°C. In cherimoya, temperature effects were relatively small: differences in growth response at the two temperature regimes were smaller than those in sugar apple. Starch content in sugar apple was also higher at 30/25°C, whereas that in stem and root of cherimoya was higher at 20/15°C. Carbon dioxide assimilation rate ( A CO 2 ) of the two species was higher at 30/25°C than at 20/15°C under low irradiance. In cherimoya, A CO 2 decreased drastically when leaves were exposed to high irradiance at 30/25°C. High temperature and irradiance increased leaf temperature to above 35°C. With increased leaf temperature, leaf vapor pressure deficit rose and stomatal conductance declined. This acclimation was associated with the reduction of photosynthesis in cherimoya. Sugar apple had higher photosynthetic activity at 30/25°C, which reflected in vigorous shoot growth. Relatively constant leaf temperature in sugar apple seemed to facilitate the high rate of A CO 2 in warm conditions. The results of this study indicate that temperature affected shoot growth and photosynthesis by influencing stomatal conductance via leaf vapor pressure deficit in cherimoya.

A Model for Phenological Development of Vietnamese Rice Influenced by Transplanting Shock

Abstract Phasic development of rice is influenced by various climatic conditions and the nursery duration. As a step toward the analysis of yield potential and yield loss in the Red River Delta, Vietnam, we conducted field trials with different nursery durations and transplanting times to develop a model for estimating heading times of a non-photosensitive cultivar CR203 in the Red River Delta. Days from seedling emergence to heading varied from 73 to 106 d, the rainy season crops having a shorter duration than the winter-spring season crops. The heading time could generally be estimated by the function of air temperature, but the delay in heading due to transplanting (transplanting shock), defined as the difference in the days from emergence to heading between transplanted and direct-seeded rice, ranged from 1 to 9 d and caused a substantial error in the heading time estimation. This variation in the delay of heading was explained as a function of the seedling age at the transplanting time. The model considering the transplanting shock estimated the heading dates in the independent data sets obtained at fields of local farmers with root mean square deviation (RMSD) of 2.15, while the model not considering the transplanting shock estimated those with a RMSD of 3.34. We conclude that this simple transplanting shock model was applicable for estimating the rice phasic development in the Red River Delta.