a) Water containing cavities are present in VBs of monocot stem
b) VBs are conjoint and closed in monocot stem, dicot leaves and monocot leaves
c) Pith is absent in both dicot stem and monocot root
d) In dicot leaf, the size of VBS are dependent on the size of the veins
How many above mention statements are correct
Answers
Answer:
Option D
ᗷᗴ ᗷᖇᗩIᑎᒪY
ᗰIՏՏ ᑕᖇᗩᘔY
A. The vascular bundle showing protoxylem vessels and parenchyma cell which dissolve leading to the formation of water cavity called lysigenous cavity such vascular bundles are found in monocot stem .
B. In monocot stem vascular bundles are found irregularly scattered in the ground tissue. Towards the periphery, the bundles are smaller in size, while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as centrifugal.
Each vascular bundle has a covering called as 'bundle sheath' formed by a single layer of sclerenchyma cells.
The vascular bundle encloses both xylem and phloem. Xylem is found towards the inner surface and phloem towards the outer surface. Cambium is absent. Hence, the vascular bundles are described as conjoint, collateral and closed.
C. Pith or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In dicots, pith is located in the centre of the stem. In monocots, it extends also into flowering stems and roots. The pith is encircled by a ring of xylem. The xylem, in turn, is encircled by a ring of phloem. The monocot root has a pith, whereas the dicot root does not. Absence of pith is the diagnostic feature of dicot root. Pith is present in dicot stem, monocot stem, monocot root and dicot stem.
D. Dicot plants have dorsi-ventral leaves which are present at an angle to the main axis and perpendicular (normal) to sunlight direction. The upper and lower epidermis are composed of compactly arranged, barrel-shaped cells without any Intercellular spaces and a cuticle on both the layers. Palisade parenchyma has 2-3 layers of elongated, compactly arranged chlorenchyma cells without intercellular spaces and with a very large number of chloroplasts but no veins. Veins represent the vascular bundles that are found irregularly scattered in the spongy parenchyma of mesophyll with the largest and the oldest one at center and is termed as midrib vein.