The primary tissues include the surface layer, or epidermis; the primary vascular tissues, xylem and phloem, which conduct water and food, respectively; and the ground tissues. The secondary tissues arise from lateral meristems, and their formation is mainly responsible for the growth in thickness of stems and roots.

plant growth The secondary vascular tissue arises from the vascular cambium, a layer of meristematic tissue insinuated between the primary xylem and primary phloem (see above Vascular tissue).

There are two basic types of root systems in plants: taproot systems and fibrous root systems. Both are illustrated in Figure below. Taproot systems feature a single, thick primary root, called the taproot, with smaller secondary roots growing out from the sides.

Phloem parenchyma

• The phloem parenchyma cells are the parenchyma cells in between the sieve tubes of the phloem, and functions primarily for food storage.
• They are present in monocot root, dicot root, and dicot stem. They are absent in monocot stem.

The bast fibres are needle-like, pointed, elongated and unbranched in their structure. The phloem fibres of hemp, flax, and jute are used for commercial purposes. The phloem fibres are composed of sclerenchymatous tissues. These are mainly absent in the primary phloem and present in the secondary phloem.

Answer : The phloem parenchyma stores food material and other substances like resins, latex and mucilage. It is absent in monocot stem.

Sclereids are found in different shapes (spherical, oval, or cylindrical) and are present in various plant tissues such as the periderm, cortex, pith, xylem, phloem, leaves, and fruits. The hardness of the shell of nuts, the coat of many seeds, and the stone of drupes (cherries and plums) is due to this type of cell.

Cambium

The majority of the monocot stem is composed of ground tissue, which primarily consists of parenchyma cells. Sclerenchyma cells are also found in regions that require extra strength. Monocot stems have vascular bundles, composed of xylem and phloem, that are scattered throughout the ground tissue.

Herbaceous plants—in contrast to trees and shrubs—are composed essentially of primary tissues. The primary body of monocots consists of vascular bundles, with no cambium, scattered in an undifferentiated parenchyma called ground tissue.

In monocots the endodermis is present around each vascular bundle. Distinction into cortex, pericycle, and pith is not seen. Vascular bundles are present in the ground tissue. Cambium is absent in monocot stems and therefore there is no secondary growth with a few exception.

Characteristics of Monocot Stem Have thick cuticle, single layered epidermis and epidermal hairs are absent. Single layered cuticularised epidermis may contain multicellular trichomes. Ground tissues are not differentiated into cortex and pith.