Studies on Vernalization of Peas

Abstract

From 1958 to 1959 the effects of low-temperature treatment in germinating seeds and young plants on the subsequent flowering of Usui peas were studied. In 1960 a further experiment was carried out to study the relation between the stage of growth in time of green-vernalization and flowering. After the treatment all materials were cultured in the greenhouse maintained above 15°C. and under the condition of 12 hours day-length. The results obtained are summarized as follows: 1. The flowering was accelerated by seed-vernalization, but not accelerated by green-vernalization. 2. Both 20 days' seed-vernalization and 30 days' green-vernalization in early stage were effective in decreasing the number of nodes to the first flower. Furthermore, it was noted that this effect increased progressively with the duration of treatment. 3. All non-vernalized plants cultured in the greenhouse maintained above 15°C flowered normally. Accordingly, there is a question whether vernalization is absolutely necessary for pea flower formation. 4. It appeared that the low-temperature treatment in the early stage of growth, such as the first leaf expanded, was most effective, but after the eighth leaf expanded green-vernalization was no longer effective.