Changes in Free Auxin Content during the Photoinduction of Short-day Plants

Abstract

The auxin content of Biloxi soybean and Xanthium italicum as measured by the standard Avena method was followed during the photoinduction period. The plant material was quick dried in an oven utilizing an infra-red heating lamp and then extracted overnight with ether at 5[degree] C. This method of drying gave results comparable to lyophilization. A decrease in auxin content was associated with the appearance of flower primordia. A plant suddenly transferred from long days to short days showed an increase in auxin content during the next few days, but this change was associated with the change in photoperiod and not with photoinduction. After the plants came into flower, their auxin content depended upon the photoperiod under which they were growing. The plants under long days, whether they were flowering or vegetative, contained more auxin than plants growing under short days. A drop in auxin content was shown to be associated with flowering but this decrease in auxin was not shown to be the cause of flower initiation.