1Division of Plant Physiology, I.I.H.R., Banglore-560006.
2Division of Biochemistry and Plant Physiology, Central Potato Research Institute, Simla-171001, (Himachal Pradesh).
In two separate investigations under short day (SD) cycles, the effects of dark periods and the substitution of 8 hr natural light with artificial low intensity illumination of about 200 foot candles on tbe tuber initiation of an obligate SD potato variety ‘Kufri Sindhuri’ previously grown under non-inductive long days, were investigated.
The tuber initation in all the plants receiving 18 hr dark period was observed after 20 SD cycles while the plants receiving 16 hr dark showed tuber initiation after 15 cycles only. In plants with SD cycles consisting 20 hr of dark period the tuber initation response was only partial and with dark periods exceeding 20 hr there was no tuber initiation. There was decrease in stolon number, tuber number and their weight as the length of dark period in the SD cycles increase from 16 to 20 hr. With increase in dark period there was reduction in dry weight of all plants and the plants also reached senescence earlier. These results indicate that all the short day cycles with dark period greater than, 16 hr were not conducive for tuberisation and development of Kufri Sindhuri.
The exposure to artificial illumination of low intensity in place of sun light during 8 hr light period of SD cycles led to a general reduction in stolon and tuber numbers and tuber yield. The weights of different plant parts and total plant weight also pointed towards the same direction. It appears that a greater part of 8 hr light during short days should be of high intensity for the proper development of potato.
