Anatomy of the Rachis of the Inflorescence of Pigeonpea (Cajanus cajan)

Abstract

The anatomical investigation of the rachis has been made on the basis of flower removal. Two different types of rachis have been investigated. One type of rachis is normal (control) which develops naturally up to maturity and another type is deflowered (treated) where flowers and buds have been removed from the basal 3 nodes and then allows the rachis to develop naturally up to maturity. After removal of flowers and buds, pods are found to be set in 4-6 nodes of the same rachis. The internal structure of rachis is more or less similar to that of the stem. Epidermis bears multicellular hairs and glandular trichomes. The vascular tissue decreases gradually from base upward. The vascular tissue become highly developed in the deflowered rachis. The cambium is highly active on its adaxial side and produces a large amount of secondary xylem adaxially and well developed sieve tube elements abaxially. Some large vessels are formed in the abaxial region of the xylem. In the middle and upper parts of the deflowered rachis, the radial dimension of xylem is several times higher than the corresponding part of the normal rachis. The vascular tissue is poorly developed in the apical part of the normal rachis. The xylem is mainly composed of fibre cells with ray parenchyma which is uniseriate or multiseriate. Pericycle is discontinuous at the basal part and gradually it forms a more or less continuous ring towards the apical part around the vascular cylinder. Tanniniferous cells are more in the normal rachis compared to that of the deflowered rachis.