Vascular Anatomy of the Floral Parts

Vascular Anatomy of the Floral Parts

Flower composition

     The flower consists of an axis (receptacle) and lateral appendages (floral parts or floral organs). The sepals and petals which constitute the calyx and corolla respectively are the sterile parts. The stamens and the carpels are the reproductive parts. The stamens compose the androecium, whereas the carpels compose the gynoecium.

Importance of floral anatomy

      The study of the vascular anatomy has helped in solving many problems of floral morphology. It has shown that many structures are not what they appear to be or what they are commonly taken to be.

      Morphologically the flower is a determined shoot with appendages, these appendages are homologous with leaves. The floral vascular skeletons, differ in no essential way from leaf stems. In the present text the flower is treated on the basis of the  homology between the flower and the shoot in their phylogeny and ontogeny.

Pedicel

The Pedicel and the receptacle have typical structure, with a normal vascular cylinder. The cylinder may be unbroken or it may contain a ring of vascular bundles. In the region where floral organs are borne, the pedicel expand into the receptacle. The vascular cylinder also expands and the vascular bundles increase somewhat in number, and finally traces begin to diverge.

The appendage traces are derived from the receptacular stele exactly as leaf traces are derived in typical stems.

Sepals

      The sepals are anatomically like the leaves of the plant. A sepal usually receives three traces derived from the same or different sources. As regards the morphological nature of the sepals, they have often been considered as equivalent to bracts and foliage leaves.

Petals

      In their vascular supply the petals are sometimes leaf like, but much more often they are like stamens. The petals may have one (very common), three or several traces.

Stamens

      A stamen generally receives a single trace which remians almost unbranched throughout its course in the filament. In the anther region it may undergo some branching.

Carpels

      The carpel is commonly looked as a leaf-like organ folded upward, i.e., ventrally with its margins more or less completely fused and bearing the ovules. This conception has been supported by the anatomy. The carpel has one, three, five or several traces. The three trace carpel is most common. The median trace which leaves the stele below the other carpel traces, is known as the dorsal trace because it becomes the dorsal (midrib) bundle of the folded organ. The outermost traces are known as ventral or marginal traces because they become the bundles that run along the ventral edge of the carpel. The ovule traces are derived from the ventral bundles.