ABSTRACT
Anatomical features of culm are also a very important feature for taxonomic identification. Internally the internodes in grasses may be solid throughout development, or may become hollow. Characteristic features of identification are represented with photographs. Both qualitative and quantitative features have been taken into consideration. Qualitative features include shape in cross section, epidermis, hypodermis, ground tissue, type of sclerenchyma, I and II IVBs, III PVB, kranz anatomy, shape of kranz arc, shape of kranz cell, chloroplast type, mesotme while quantitative features include features like cross sectional area, number of vascular bundles, size of vascular bundles, size of metaxylem, number of kranz cells were considered in study. Also based on the presence or absence of kranz anatomy, the studied species have been divided into two categories.
Five different major types of epidermis were identified among the studied grass species on the basis of their shape and cuticularization: barrel shaped, rectangular shaped, square shaped, elongated shaped, and round shaped.
Vascular bundles are found irregularly scattered in the ground tissue. Toward the periphery, the bundles are smaller in size while toward the center, they are larger in size. The smaller bundles are younger, while the larger ones are older. Each vascular bundle has a covering called bundle sheath formed by a single layer of sclerenchyma cells. The cambium is absent. Hence the vascular bundles are described as conjoint, collateral, and closed.
Three types of vascular bundles are present: (1) Internal vascular bundle (IVB)—I and II vascular bundles are present toward the center so they are known as IVB. I and II IVB are organized in one to three concentric circles. (2) Peripheral vascular bundles (PVB)—vascular bundles are present toward the periphery. Third-order peripheral vascular bundles (III PVB)—inconspicuous proto and metaxylem cells. Nine types of I IVB are present, seven types of II IVB are present, one type of III PVB is present. The culms of a few grass species show the presence of chlorenchyma. 342Chlorenchyma surrounds the III PVB. It is in the form of arc, so it is known as Kranz arc. Kranz anatomy is observed only in species like Eragrostis, Dinebra, Cenchrus setigerus, Dactyloctenium sps., Tragus biflors, Perotis indica, Tetrapogon sp., etc. This chlorenchyma is radial chlorenchyma. The shape of Kranz arc was: straight, half circle, horseshoe shaped, and circular shaped.
Kranz arc, radial cholrenchyma, culm outline and chloroplast shape and position, are some of the culm anatomical features suggested to be useful for inferring phylogenies. Based on all above characters a dichotomous key has been prepared and statically analyzed using cluster analysis.
