Correlation between form, structure and habit in some lianas

Abstract

1. The present paper deals with the gross anatomy and certain mechanical properties of the stem of sixteen lianas with anomalous secondary growth in comparison to that of an erect plant.

2. An analysis developed from mechanics considerations shows clearly that liana stems have adopted themselves to some well-known engineering principles in developing their internal structure to counteract the stresses and strains caused by the natural external forces of wind, rain, light, etc.

3. Apart from the size of the pith, the shape of the pith (circular, oval) and its eccentricity with respect to the xylem cylinder also affect the flexibility.

4. The order of increase of flexibility as predicted on theoretical considerations agrees well with the order obtained from the experimental results. Further, a close relation between flexibility and water content of these plants exists.

5. A detailed study of three varieties ofBougainvillea lends support to the viewpoint stressed recently by Esau and Cheadle (1969) that complimentary cambial strips develop just adjacent to the secondary phloem and the cambium is bi-directional in this plant.