Abstract: | Extracts of small and mature-size lupin pods yielded four substancesaffecting the growth of wheat-coleoptile sections: one acidpromotor (A), two acid inhibitors(B and X), and one neutralinhibitor(Y). Inhibitor B was extremely active, however, coleoptile sectionsshowed no signs of toxic effects; they resumed growth at a rapidrate after rinsing them and adding ß-indolylaceticand (IAA) to the medium. 1 µg of IAA was required to counteractthe effect of B extracted from 230 mg. Of tissue.On an equal fresh weight basis the inhibiting action of Bin lupin pods was 5001,500 times more potent than thatof inhibitor ß in etiolated pea seedlings. Small pods of plants infected with pea-mosaic virus yielded3 times the amount of A of healthy plants (equivalentto 1 µg. IAA 0.3 µg. IAA per 25 g. of tissue respectively),and approximately the amount of B. Mature podsof virus-infected plants again yielded moreA,but also 2? times more B than pods of healthyplants. Healthy pods yielded more A than virus-infectedpods, and there was no difference in X. A lupin abscission test was developed and the effects of proximaland distal application of -naphthyl acetic acid (NAA) are presented,and discussed with respect to results of other abscission tests. A accelerated abscission when applied proximally,and delayed or prevented it when applied distally. Bstrongly accelerated abscission when applied in either way.A possible mechanism explaining the abscission-inducing effectof developing pods on later flowers is discussed in terms ofthe substances A and B. The partlyprevented abscission observed on virus-infected plants was foundto agree well with the proposed mechanism. |