In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate, and gives rise to primary tissue.

Plants that grow from stem cuttings: Foliage shrubs like Golden Duranta, Acalypha, Crotons; Kitchen herbs like Rosemary, Thyme, Mint etc. Apart from these many herbaceous annuals, climbers and creepers, and hedge plants and many flowering trees like Gliricidia can be grown by stem cuttings.

apical bud

The primary functions of the stem are to support the leaves; to conduct water and minerals to the leaves, where they can be converted into usable products by photosynthesis; and to transport these products from the leaves to other parts of the plant, including the roots.

vascular cambium

Primary growth is controlled by root apical meristems or shoot apical meristems, while secondary growth is controlled by the two lateral meristems, called the vascular cambium and the cork cambium. Not all plants exhibit secondary growth.

Most primary growth occurs at the apices, or tips, of stems and roots. Primary growth is a result of rapidly dividing cells in the apical meristems at the shoot tip and root tip. Subsequent cell elongation also contributes to primary growth.

Yes primary and secondary growth occurs in same plant but not simultaneously. Primary growth occurs when the plants are young means the growth of roots and stems in length with the help of apical Meristem is primary growth.

In plants undergoing secondary growth, the pericycle contributes to the vascular cambium often diverging into a cork cambium. In angiosperms certain molecules within the endodermis and the surrounding vasculature are sent to the pericycle which promotes the growth of the root meristems.

Normally secondary growth takes place in roots and stem of dicotyledons and gymnosperms. Due to lack of cambium in monocotyledons, secondary growth is absent. But exceptionally, secondary growth takes place in some monocotyledons, such as palm, Yucca, Dracaena etc.

In general, monocots do not undergo secondary growth. If they do increase in girth (like palm trees and yucca plants), it does not result in the development of a secondary xylem and phloem, since monocots don’t have vascular cambium. An increase in girth without secondary growth is referred to as anomalous thickening.

Secondary growth is a feature of gymnosperms and most dicot plants (dicot woody plants). Only a few monocot plants show secondary growth and none pteridophytes (ferns and the likes).

These tissues are formed by meristems, vascular cambium and cork cambium respectively. Secondary growth does not occur in monocots because monocots do not possess vascular cambium in between the vascular bundles.

Root cap is absent in.

In particular, secondary growth is substantial for constant plant growth and the remodeling of body structures. As an important meristem involved, the vascular cambium forms a cylindrical domain below the organ surface producing tissues for long-distance transport and mechanical support: wood (xylem) and bast (phloem).

Secondary growth is initiated by the activity of the vascular cambium as far as the steler region is concerned. This intrafascicular cambium is absent in the open vascular bundles of the monocot stem, thus the process cannot take place .

Collenchyma

Dicot root When cells of the vascular cambium divide, they differentiate into secondary growth xylem and phloem, which increases the girth of dicot roots and stems. Monocots do not have vascular cambium.

It has abundant plasmodesmata for the lateral conduction of food. Phloem parenchyma is absent in most of the monocots. Thus, the monocot stem is the one among the options that do not contain phloem parenchyma.

Phloem parenchyma

Phloem parenchyma is absent in most of the monocotyledons. Phloem fibres (bast fibres) are made up of sclerenchymatous cells. These are generally absent in the primary phloem but are found in the secondary phloem.

Elaters are structures present in plants. They are generally present to facilitate spore dispersal (liverworts) but are absent in mosses and spore dispersal is controlled by the peristome.

Hence the bryophytes lack the true roots and the vascular tissue. Note: Like all land plants, bryophytes have life cycles that alter in the generations like gametophyte and the sporophyte.

The sporophyte, or asexual generation, forms a tapered cylinder. Hornworts differ from other bryophytes in having a region of continuous growth at the base of the sporophyte, and a large irregular foot. The stalk that attaches the foot to the spore-bearing capsule in liverworts is absent in hornworts.

Foot and seta is absent in sporophytes of anthoceros.

Traditionally, hornworts have been classified as bryophytes, together with mosses (division Bryophyta) and liverworts (division Marchantiophyta).

General structure Anthoceros form small rosette like plant. Unicellular rhizoids are attached to the underside of the thallus. Small mucilaginous cavities are present on the ventral side. These cavities contain colonies of a blue green alga like Nostoc.