Abstract
Changes in leaf-colour are one of important indication on rice cultivation, because the leaf-colour is considered as a reflection of metabolic activity in the plant body. Some methods have been tried so far to express the leaf-colour of rice plants. However, all these methods have developed based on individual leaves and they are troublesome in measuring. Therefore, authors have tried to find out a suitable and easy method for expressing the leaf-colour in mass under field conditions., not in individual leaves, obtaining a fair success. The method and results obtained are summarized as follows: 1. For expressing the leaf-colour a standard colour plate is made by using some commercially available greenish embroidary threads. The plate has been composed of 5 grades of greenish colour and each colour on the plate is named 1 to 5, pale green to dark green, respectively, as shown in Fig. 1. 2. The standard colour plate is set, in a given field, just above the uppermost expanded leaves. Then observers stand at the distance 5∼7 meter away from that plate, turning their back on the sun, and choose the most resembling leaf-colour grade on the plate to the actual leaf-colour in mass on the field. When the leaf-colour of leaves falls intermediate between two values of the grade on the plate, it should be expressed by an intermediate value between two values. 3. So high correlation coefficients have been found between observed values of leaf-colour grade on the plate and nitrogen contents in leaf blades of upper leaves that observed values of leaf-colour may be used as an estimate of nitrogen content in leaf blades. 4. Since the method above mentioned for expressing the leaf-colour is very simple and easy, every one might be able to use it, if only the embroidery threads or similar ones were available. 5. The authors have been trying to explore a new standard colour plate, which will be developed on the basis of the three attributes of colour, i.e., Lightness, Hue and Saturation of actual leaves.
