In this article we will discuss about the evolution of stelar forms in vascular plants. The well known genus Rhynia represents the simplest kind of vascular plant. It is rootless, leafless and the axis is dichotomously branched. A stele runs through the centre of stem. The cells in the very centre of stele consist of tracheids only and this xylem [...]
In this article we will discuss about the four main types of root stem transition in angiosperms. Type A (Fig. 16.1.1A-1E): This type is represented by Dipsacus, Mirabilis and Fumaria. In the root there are four strands of phloem and four strands of xylem with exarch protoxylem. They are arranged radially. The stem shows four conjoint collateral vascular bundles with [...]
In this article we will discuss about the root stem transition in plants. The change in arrangement of vascular tissues of roots having separate strands of phloem and xylem with exarch protoxylem to collaterally placed phloem and xylem with endarch protoxylem of stem is commonly referred to as root-stem transition. In higher plants root and shoot form a continuous axial [...]