Which of the following is without exception in angiosperms? (a) Presence of vessels (b) Double fertilisation (c) Secondary growth (d) Autotrophic nutrition
Option B In angiosperms presence of vessels is not an universal feature as there are certain angiosperms where vessels are absent e.g., Wintera,Trochodendron etc. Secondary growth is increase in the girth or diameter of axis (root and stem) of the plant by formation of secondary tissue by the activity of lateral meristem. It occurs in dicotyledons of angiosperms and gymnosperms. But in monocotyledons of angiosperms the primary plant body is complete in itself and doesn’t produce any secondary tissue. Autotrophic plants are those which synthesise their organic food themselves by the process of photosynthesis. But certain angiospermic plants have heterotrophic mode of nutrition. E.g. Rafflesia, Orobanche, Striga are root parasites. But double fertilization is universal in all angiosperms. It involves fusion of one male gamete with the egg cell and another male gamete with the diploid secondary nuclei.
