Studies on the floral induction of slow bolting varieties in spinach. I

Effect of chemical vernalization and low temperature treatments of seeds

Abstract

1. In order to obtain the basic data for promotion of flowering in slow bolting spinach, the effect of chemical vernalization (auxin and low temperature treatment) and low temperature treatments of seeds to floral initiation were examined with the King of Denmark and other three varieties. Dry seeds were treated with auxin (1 p. p. m. naphthaleneacetic acid) for 24 hours. The temperature treatment was continued for 2 weekes in 3±1°C. Those seeds were sown in spring (March 5), summer (June 15) and fall (Oct. 5).
2. The time of initiation of floral primordia of the four varieties were markedly accelerated by a combination treatment of auxin followed by a low temperature and single treatment of low temperature, as compared with non-treatment controls under the three respective season.
3. The promotion of earliness concerning the bolting and flowering was also markedly shown in plants which received treatments, mentioned above, but showed the differences on the development of flower-stalks with four varieties under the short-day conditions in fall or winter.
4. In the first experiments (sown in March 5), the plants of the King of Denmark variety which received vernalization tretment passed over normally the course of bolting, flowering and fruiting, and obtained seeds amounting to 19.8cc. in average, per plants under the greenhouse conditions, and germination of seed showed the higher percentage. While, the controls not in treatment formed very little flower stalks.
From these facts, it will be clear that the acceleration of floral initiation of spinch is induced by immediate effect of vernalization, and that the after-effect of this treatment for seeds may alter the photoperiodic responces of this crops.