Growths of mulberry lamina, petiole and internode and their relationships

Abstract

Changes in lamina, petiole and internode growth in the mulberry (cv. Shin-ichinose) were investigated and the relationships between their growths and temperature were considered. The duration of internode growth was shortest and the duration of the petiole was longest. The growth duration of the lamina had a highly negative relationship to the temperature at the leaf appearance and the growth duration of the internode had a highly negative relationship to the temperature more than ten days before the internode appearance. The growth duration of the petiole had less of a relationship with temperature. Some petioles elongated again after the growth stopped. The lower the position of the petioles, the longer the elongation became. The temperature effects on the internode length were different among three temperature conditions. At 20°C, first internode length was very short and the length increased steeply until about the tenth internode. After that, the length decreased gradually to about the 20th internode and the length became almost constant. At 28°C, first internode length was longer than at 20°C and the length increased gradually until about the tenth internode. After that, the length became almost constant. At 24°C, a change in the internode length showed middle style of the changes in the length at 20°C and 28°C. From the results, it was considered that the leaves established a vertical position during the early growth of their attached internodes, and that the lamias improved their position to intercept light by late growth of their attached petioles.