A bstract. Time-sequence analyses of carbohydrate breakdown in germinating rice seeds shows that a rapid breakdown of starch reserve in endosperm starts after about 4 days of germination. Although the major soluble carbohydrate in the dry seed is sucrose, a marked increase in the production of glucose and maltooligosaccharides accompanies the breakdown of starch. Maltotriose was found to constitute the greatest portion of the oligosaccharides throughout the germination stage. a-Amylase activities were found to parallel the pattern of starch breakdown. Assays for phosphorylase activity showed that this enzyme may account for much smaller amounts of starch breakdown per grain, as compared to the amounts hydrolyzed by ay-amylase. There was a transient decline in the content of sucrose in the initiall 4 days of seed germination, followed by the gradual increase in later germination stages. During the entire germination stage, sucrose synthetase activity was not detected in the endosperm, although appreciable enzyme activity was present in the growing shoot tissues as well as in the frozen rice seeds harvested at the mid-milky stage. We propose the predominant formation of glucose from starch reserves in the endosperm by the taction of a-amylase and aocompanying hydrolytic enzyme(s) and that this sugar is eventually mobilized to the growing tissues, shoots or roots.Recent biochemical studies have elucidated the mechanism of carbohydrate metabolism in fatty seeds with particular emphasis on the fat-carbohydrate conversion and its control (3). There have been many classical works on the breakdown of reserve polysaccharides in starch-bearing cereal seeds (10). It is generally accepted that the amylolytic breakdown of starch may account for the major metabolism of carbohydrate in the endosperm tissues of these plants (1,20,21). A rapid increase in the a-amylase activities in the endosperm of germinating barley seeds was observed many years ago, and currelnt biochemical studies have demonstrated the mechanism of the gibberellic acid-induced synthesis of a-amvlase in the aleurone layers of cereal grains, resulting in the hydrolysis of the starch reserve in the endosperm tissues (7,16,17,(23)(24)(25) significance of the data is discussed in ternms of the physiology of germinating rice seeds. Materials and MethodsRice Seed Geriaiziitionz. Seeds of the rice plailt, Oryzae satiza L. var. Fujiminori, were soaked in a disinfectant solution (0.1 % Takeda-Mer, Takeda Pharmaseutical Co. Ltd ) for 1 hr at room temperature. After thoroughly rinsing the seeds in running water, they were sowed on a wet filter paper placed in a deep Petri dish (d = 20 cm). The seeds were then germinated in a temperature-controlled chamber (300) in the dark. In order to avoid fungus infection during germination, all seeds in one dish were used for a single analysis. For the gibberellic acid (GA) treatment, rice seeds were soaked in GA (1 ,ug/l) solution (Kyowa Hakko Co. Ltd.), and germinated as described above, except filter paper in a Petri dish was wet...

The physiological changes in green bananas (cv. Sin‐zun), which are very sensitive to chilling injury, were studied during and after exposure to low temperatures (4±1°C, 6±0.5°C) for various periods. While the fruits injured by chilling did not fail to produce CO2 and ethylene, the pattern of both CO2‐ and ethylene production in these chilled fruits (9 and 15 days at 6°C) after transfer to 20°C was not normal. The contents of acetaldehyde and ethanol in chilled fruits, both in peels and pulps, increased with the advance of chilling, injury. There was an accumulation of α‐keto acids in the peels of chilled fruits. Only half the conversion of 14C (fed as succinic acid‐1, 4‐14C) to citric acid and isocitric acid was observed in chilled tissues as compared with healthy ones; the activity of citrate synthase in banana peels appears therefore to be inhibited by chilling injury. A histological study of the tissues showed that the browning substances (polyphenols) present in chilled fruits accumulate around the vascular tissues.

A liquid scintillation counting apparatus that enables highly accurate measurements of 14C has been constructed at the Solar-Terrestrial Environment Laboratory, Nagoya University. The main aim of the project is high precision year-by-year measurements of the 14C content in tree rings of an old cedar tree from Yaku Island, Japan. We present the results of 14C measurements on tree rings from the Agematsu region for recent decades to confirm the validity of the system.

A method was devised to measure chilling sensitivity in a series of species and hybrids of Passiflora having a range of climatic requirements. Leaves from plants which had been grown under 25°C day/18°C night were chilled at 0°C in the dark. At the same time, leakage of electrolyte from thin strips of these leaves was measured at 0°C using conductivity. Two main stages of leakage were found: a relatively slow rate (stage 1) which was followed by a high rate (stage 2), during which most of the electrolyte was lost from the tissue. Potassium was the principal cation lost from the tissue, and its leakage was proportional to that of total electrolyte during the time course of leakage. Stage 2 occurred at about the same time as obvious lesions appeared on whole leaves, and apparently signified lethal chilling injury. When different species were compared, those which had originated from the tropical lowlands (P. maliformis L. and P. edulis Sims forma flavicarpa Degener) were killed in less than 10 days, but those tolerant of cooler climates (P. caerulea L. and P. edulis Sims) survived much longer. From the behaviour of a number of species and hybrids, the rate of leakage during stage 1 was related to the time taken to reach stage 2. Resistance to chilling in the species and hybrids examined was not an all-or-nothing property, but showed a gradual increase in the series: P. edulis forma flavicarpa < P. maliformis < P. cincinnata Masters < P. edulis < P. caerulea, with some hybrids occupying intermediate positions.

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