Physiological and Ecological Studies on the Secretory Function of Essential Oil in Pelargonium species : VII. Seasonal fluctuation of the percentage of oil yield and its influential elements

Abstract

This paper presents the study of the seasonal variation of percentage of oil yield of Pelargonium and the relations of its external as well as internal environments and the influential elements of the variation. The material used in the test was P. roseum "France" and the analyses of the elements was made from the data compiled during the period from 1956 to 1958. 1) In seasonal fluctuations of the percentage of oil the air temperature was the prime controlling influential factor, and the humidity and the amount of solar radiation was secondary (Fig. 1, Table 1). 2) Between seasonal and leaf age variations of the percentage of oil and the air temperature there existed a high positive correlation coefficient. To state further the characteristics : 【○!a】 The percentage of oil of the young leaf had a higher correlation coefficient than the old leaf and was more sensitive to the air temperature than the latter. 【○!b】 The percentage of oil during the period from May to August was more sensitive to the variation of the air temperature in comparison with that during the period from September to November. 【○!c】The percentage of oil during the period from 0ctober to November was somewhat higher than that during the period from May to June irrespective of generally higher temperature during the latter period. The cause of this phenomenon was presumed that the secondary influential elements aforesaid, that is humidity, rainfall, number of hours of sunshine, etc. gave favourable conditions to the secretory function of essential oil(Table 2 & 3, Fig. 2). 3) Between the rise of air temperature and the percentage of oil there existed a parabolic relation and it reached the highest limit at the temperature from 28 to 29°C (temp. at 9 a.m.) and higher temperatures caused decrease of the percentage of oil yield (Fig. 4). 4) Appropriate fertilizers, soil moisture, soil pH, etc. were effective in increasing yield of grass, but no significant effect was found for increasing the percentage oil yield. 5) The result of the study of the relations among the plant age, the duration of nursing and the percentage of oil showed that there was no difference, but about equal percentage of oil yield for the same period (Fig. 5∼8). From the foregoing analyses the important factors influencing the percentage of oil yield were to be concluded as the atmospheric elements. The biochemical mechanism relating to the fluctuation of oil yield are now under study