Underground plant movement III. The corm of Sauromatum guttatum (Wall.) Schott (Araceae)

Abstract

Summary Underground movement in some Araceae shows that in cormous plants, both root contraction and shoot growth are important factors. In depth regulation, two kinds of movement can be distinguished. To secure an underground position it is necessary to compensate the upward growth of vertical corms. Thus, in Sauromatum , either a defined position is maintained, or small downward movement of adult corms occurs. Greater movements are necessary to reach an ecologically useful position. The observation of Sauromatum seedlings makes clear that at this stage of plant life the force involved in downward movement is relatively low. The corm is very small and, on turning, a channel effect can occur. In Arum and Arisarum , even adult corms show greater movement. This occurs when the normally horizontally growing corm is re-oriented into the direction of contractile root activity. This produces summation of both types of movement. Simultaneous occurence of root activity and corm growth is not possible in the vertical position of adult Sauromatum corms. However, lateral buds are normally positioned at an angle to the mother corm initially, and move in a way similar to that of Arum .