SOME CHEMICAL CHANGES ASSOCIATED WITH THE TRANSITION FROM VEGETATIVE TO REPRODUCTIVE GROWTH OF WINTER WHEAT

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Abstract
Winter wheat (Brill, a selection of Turkey Red) was vernalized at 2[degree]C for 67 days. The vernalized seedlings were transplanted to pots of soil and grown under a daily photoperiod of 3 hrs. The 8-hr. photoperiod prevented the plants from entering the reproductive phase of growth and a total of 9 leaves were formed. As the 10th leaf emerged, the plants were switched to a 14-hr. photoperiod. Within 10 days the plants jointed and floral primordia could be detected. Plant samples were cut at 2- to 4-day intervals while the plants were on the 8-hr. photoperiod. After switching to the 14-hr. photoperiod, plants were cut daily. Changes in green wt., dry wt. and plant height were followed during the growth of the plants. Ascorbic acid and chlorophyll were detd. on fresh plant tissue and riboflavin and total N on dried plant tissue. The % ascorbic acid, chlorophyll, riboflavin and N was highest during the early growth of the plants and decreased as the plants matured. Several days after the plants were switched from short- to long-day a series of rhythmic changes in conc. of total N, riboflavin, ascorbic acid and chlorophyll were detected in the leaf, stem and tiller tissue. These chem. changes were evident before any external evidences of flowering were observed. The N, riboflavin and chlorophyll behaved similarly following the switch-over. The fluctuations in ascorbic acid conc. occurred a day earlier than the fluctuations in conc. of N, riboflavin and chlorophyll.