Studies on Phloem Exudation Fromyucca Flaccidahaw. Ii. The Translocation of Assimilates

Following the feeding of 14C02 to a mature leaf of Yucca flaccida Haw. a number of exudate fractions were collected from a bleeding inflorescence Stalk. The maximum amount of activity was collected on the third day after the application of the 14C02. In all the exudate fractions sucrose contained about 90 per cent of the radioactivity present. The 14C-content of the exudate exhibited a pronounced daily rhythm. The fractions which exuded during the night contained concentrations about four times those of the exudates collected during the hours of daylight. In contrast, the total dry substances and total sugar contents only showed slight daily variations. Apparently the various leaves or other parts of the plant contribute with slightly different rhythms to the solutes of the exudate.