Japanese Journal of Crop Science

Die Temperature-summe in Period als frostfrei Jahreszeits ist ein allgemeines Index des Temperaturklimas in den warmeren Jahreszeiten. Sie wird durch die monatliche mittlere Lufttemperatur und die Frostdata in den vetreffenden Standorten ausgerechnet. Deren Isopleth im nordlichen Teil 0stasiens stellen das Temperaturklima in den warmeren Jahreszeiten in jeden Standorten besser da als andere Konstanten wie jahrliche mittlere Temperatur, Temperatur in gewissen Monaten, die Lange der Dauer der frostfreien Jahreszeiten oder die Lange der Vegetations-periode. Unter Rucksichtsnahme der Prezipitation, Sonnenschein und anderen okologische Faktoren, ist sie bei Bestimmung des klimatischen Belts und der Grenze der Anpflanzung von Sommergetreiden verwendbar.

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1. Since 1941, we have made experiments on the photopeiodism in several kinds of fibre crop plants, demonstrating that each of them might be classified into several groups according to their response to light exposure. 2. The kenaf plant (Hibiscus caunabinus L. ) is generally known as a short day plant. But, by our experiments, the effects of day length on it were found to vary according to its variety. 3. The colour of the stem and leaf of kenaf were conspicuously changed by shortening or lengthening the daily pcriod of illumination. The shape of the leaf blade, especially the number of its lobes, was also affected (Figs. 2-4). These facts may not only be of importance for crop scientific and breeding investigations of the plant, but also be interesting from genetical and ecological points of view. 4. Influence of day length and temperature on jute plant (Corcchorus eapsularis L. ) proved also various according to its variety. Its cultivation, however, may generally be restricted to the localities of lower latitudes. In the regions of hign latitudes, no varieties may produce seeds of complete maturation. 5. Chinese jute (Aburilon avicennae G. ) belongs to the short day group, but can bloom by somewhat longer daily illumination, being cultivable over fairly wide ranges of latititudes, provided with sufficiently high temperature. The Cultivation of the plant and retting and cleaning of the fibre are very simple. 6. Ramie (Boehmeria nivea H. et ARN. ) inverses in sex by day length control. When illuminated with short day, grows lower in the height like many other crop plants.

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