Question

Vascular bundles of Cucurbita stem are
A. Collateral
B. Bicollateral
C. Radial
D. Concentric

Answer 1

Hint: Vascular bundles are made of xylem and phloem. They form an integral part of the vascular system in plants. The vascular system in plants functions to transport and minerals. The vascular bundles can be of different types based on the arrangement of xylem and phloem.

Complete step by step answer: The transport system of plants comprises xylem and phloem. Xylem helps in transporting water from the roots to all parts of the plant. Phloem serves to transport the carbohydrates formed as a result of photosynthesis. The process of transport of water and nutrients in plants is known as translocation and is mediated by the vascular system. Vascular system comprises xylem and phloem arranged in a form of bundles called vascular bundles. Vascular bundles are of various types depending on the arrangement of xylem and phloem. They can be described as follows:
Collateral – the xylem and phloem lie side by side. Cambium tissue may be present or absent. If cambium is present, the condition is known as open collateral. If the vascular bundle lacks xylem, the condition is known as closed collateral.
Bicollateral – If the phloem is present on both the peripheral and inner side of xylem tissue, the vascular bundle is known as Bicollateral. The strip of cambium between the peripheral phloem and xylem is the outer cambium. The strip of cambium between the inner phloem and xylem is called the inner cambium. Bicollateral vascular bundles are always of open type since cambium is present.
Concentric – When either xylem or phloem is surrounded by the other, the vascular bundle is of concentric type.
Radial – If the primary xylem and phloem are separated by nonvascular tissues, it is known as Radial vascular bundles.
Cucurbita belongs to the family Cucurbitaceae. The plants of this family are herbaceous vines in nature and grow with the help of tendrils. The common plants of this genus include squashes, pumpkins, gourds and are grown worldwide.
The transverse section of Cucurbita stem shows it to have a wavy margin with distinct ridges and furrows. The vascular bundles are arranged in two rings – the larger ones in the center and the smaller ones towards the edges. The vascular bundles are of bicollateral type.
Hence, option (b) is correct.

Note: Transport of water and minerals in plants are mediated through the xylem and phloem respectively. The tissues are grouped together forming vascular bundles. Based on how these two tissues are arranged, the vascular bundles can be of various types. The genus Cucurbita comprises the gourd family. They are dicotyledonous plants displaying the bicollateral arrangement of vascular bundles.