Question

In which part of Cycas diploxylic vascular bundles are found?
A. Root
B. Stem
C. Leaflet
D. Rachis and leaflet

Answer 1

Cycas is a genus of plants that belongs to the Cycadophyta lineage, which is not linked to palms, ferns, trees, or any other current plant group. They are evergreen perennials that reached their peak diversity during the Jurassic and Cretaceous periods, when they were found practically everywhere on the planet. When the non-avian dinosaurs became extinct at the end of the Cretaceous, so did most of the Cycas in the Northern Hemisphere.

Complete answer:
Option A: A diploxylic vascular bundle is a circumstance in which two types of xylem, centripetal xylem (present towards the centre) and centrifugal xylem (present further from the centre), coexist in some plants (present towards outside).
So, option A is not correct.
Option B: The leaf trace has just centrifugal xylem in the region of the stem cortex, making it endarch.
So, option B is not correct.
Option C: The rachis and leaflets are connected by diploxylic vascular bundles. The leaf trace is endarch because it only has centrifugal xylem in the stem cortical area. These traces enter the leaf as the rachis divides, the centripetal xylem grows, and the leaf is in the exarch phase. The leaflet has a single midrib bundle and is diploxylic.
So, option C is not correct.
Option D: Diploxylic vascular bundles run through the rachis and leaflet. The leaf trace has just centrifugal xylem in the region of the stem cortex, making it endarch. As the rachis divides, the centripetal xylem develops, and the leaf is in the exarch condition, these traces penetrate the leaf. The leaflet has a diploxylic state and a single midrib bundle.
So, option D is correct.

Hence, Option D. is the correct answer.

Note:
The plants are dioecious, and the Cycadaceae family is unique among the cycads in that female plants produce a bunch of leaf-like structures called megasporophylls, each bearing seeds on the lower borders, and male individuals produce pollen cones or strobilus. The persistent petiole bases surround the caudex, which is cylindrical. Most species have separate branched or unbranched trunks, but some species have a subterranean main trunk with a leaf crown that appears to emerge directly from the ground. Foliage leaves and scaly leaves are the two types of leaves. The leaves are pinnate (or, less frequently, bipinnate) and spirally organised, with thick and hard keratindose.