Secondary growth on the trunk of dicots: what you need to know (2023)

Secondary growth of a dicot stem:Some trees like itEucalyptus,Bombak, neem, mahogany, etc. are exceptionally higher than others. They will also have thicker and woody stems. But do you know how these trees develop such thick trunks? This thick stem is an example of the secondary growth of a dicot stem.

Secondary growth is the formation of secondary tissue from the lateral meristem. This will increase the diameter of the stem. Secondary growth usually occurs in the stems and roots of perennial gymnosperms and dicotyledonous plants such as trees and shrubs as a result of cell division in the cambium. The thickness of the dicot stem increases due to the addition of secondary tissues separated by the cambium and cork cambium in the stellate and extrastellar regions. Scroll down to learn more about the secondary growth of dicot stems.

Secondary growth in the definition of a dicot stem

The formation of secondary tissue leads to an increase in the range of the so-calledSecondary growth in the trunk of a dicotyledonous plant. Secondary tissue consists of two types of lateral meristem:vascular cambiumIPeta Kambij.

Arihant-Biologie Handbook

It is produced by the vascular cambium and the corky cambiumSecondary vascular tissueIPeryderma, this is. Secondary trunk growth increasesstem diameter. It happens in...perennial gymnospermsand dicots and many shrubs. Secondary growth is the formation of secondary tissuelateral meristems. For woody plantssecondary tissuemake up most of the plant.

Image: ZoomEucalyptusHolz

Examples of secondary growth of dicotyledonous stems

Now the students know the answer to the question: "Describe the process of secondary growth of the dicotyledon shoot." Secondary growth usually occurs in most woody tree trunksMarlon,Sissoo Dalbergii,acacia, Tikovina,a creature, mango, nimm,Eucalyptusetc. Secondary growth also occurs in tomatoes, potatoes, etc., although they are not woody.

As we all know, in monocotyledonous plants, there is no secondary growth due to lack of cambium, but palm,Yucca,dracenyetc. some are exceptions to the secondary growth of monocots.

Secondary growth in the stem process of dicotyledonous plants

The normal secondary growth of the dicot stem increases the diameter of the plant stem due to the activity of the vascular cambium.

A. Formation of the cambium ring

1. Vascular bundles in the stems of dicots are connected, lateral and open (presence of cambium) and arranged in a ring.
2. The cambium present in the vascular bundles between the xylem and the phloem is called the cambiumBundle or intra-bundle cambium.
3. In secondary growth, certain cells are formedcore raysthose present between the vascular bundles also become meristematic and are referred to asInterfascicular cambium.
4. Both the intrafascicular cambium and the interfascicular cambium together form a complete ring calledKambiumring.
5. The cambium ring provides secondary growth.

Abb: Kambiumring

B. Secondary Tissue Formation

1. The cambium ring cuts off the cells on both sides. It forms secondary phloem on the outside and secondary xylem on the inside.
2. The amount of secondary xylem cut is greater than that of secondary phloem.
3. The cambium ring migrates towards the periphery as more secondary xylem cells are formed towards the center.
4. The original xylem and primary phloem that were originally closed are removed in the formation processsecondary xylemISecondary phloem.
5. Layers of secondary tissue are gradually and continuously added to both the inside and outside of the cambium throughout the life of the plant.

C.Formation of secondary core rays

1. There are two types of cambial cells:Spindle shaped initialsIRay's initials.
2. Spindle-shaped initials are vertically elongated cells from which vertical elements such as vessels, tracheae, etc. are formed.
3. The initials of the rays are horizontal and smaller. They create rays in the secondary tissue and produceParenchymzellen.
4. Primary and secondary phloem are progressively degraded by the continuous formation and accumulation of secondary xylem.
5. However, the main xylem remains intact near the center.
6. In some places, the cambium forms a narrow parenchymal belt that passes radially through the secondary xylem and secondary phloem. These are the so-calledSecondary core rays.
7. Secondary medullary rays provide radial conduction of food from the phloem and water and mineral salts from the xylem.

Image: Secondary Core Rays

D.creating annuals

1. The activity of the cambium is influenced by the changes of the seasons.
2. In the spring, due to the favorable weather and the associated increased activity of the cambium,SpringwoodLubearly woodeducated. In the case of slats, the clearances are wider.
3. In winter or autumn, the cambium is less active and forms narrower and smaller vessels. The wood that grows in winter and autumn is called woodturn it offIautumn treeLublate wood.
4. Alternate spring and fall tree of the yearannual ringLubgrowth ring. This is a reliable way to determine the age of a tree (by counting the number of years). The science of counting the age of trees is calledDendrochronologia.

Image: Year ring

MI.core and white formation

1. Secondary wood on the inside loses conductivity for old trees that have had sufficient secondary growth.
2. The central part of the stem is dark, hard and malleable due to the presence of tannins, resin, gum and essential oils. This region is calledKernholzaLubKernholza.
3. Due to the formation of tylose in the vessels, the marrow loses its conductive function. In this way, the heart provides mechanical support to the trunk.
4. The outer part of the hull is lighter and softer and takes over the function of conducting water and minerals. This region is calledSplintholzLubBiel.

Photo: Cross-section of the trunk with heartwood and sapwood

F. Secondary growth in the extrastellar region due to the activity of the cork cambium

1. The increase in the diameter or thickness of the petioles is a consequence of the activity of the vascular cambium.
2. This leads to the breakdown of the outer cortical and epidermal layers, which must be replaced to form new protective cell layers.
3. The outer cortical cells or some subcutaneous cells become meristematic and begin to divide to form a corky cambium or phellogen.
4. The cork cambium then divides to form secondary tissue on the inside and outside.
5. The cells excised from the outside are the phellem or cork cells, and those inside make up the secondary cortex, or dermal cortex.
6. This is whyfelogen,FilIFelodermasummarizePeryderma.

Image: Non-stellar secondary growth in a dicot stem

Abb: Korkambij

G.crust formation

1. The bark stands for all tissuesvanivascular cambium.
2. The crust is the crust that forms at the beginning of the seasonwaterLubsoft peeland at the end of the seasonlateLubhard peeleducated.
3. This layer isas suberizedIimpermeablePour.

H.creating spiracles

1. Some of them are preservesloosely spaced areasI amPeryderma.
2. Due to the greater activity of some parts of phellogen, phelem cells are cut off very quickly, which makes them loosely distributed and have many intracellular spaces. your helpgas exchangeITranspiration.
3. These loosely arranged cells are calledComplement cells.
4. Spiracles are a feature of woody stems.

Sl.: spiracle

Diagram of the secondary stem of a dicotyledonous plant

Photo: Secondary growth on the trunk of a dicotyledonous plant

The difference between Springwood and Autumnwood

Below is the difference between Springwood and Autumnwood:

The difference between white and core

The following is the difference between sapwood and core:

Abstract

Secondary growth occurs in most dicot stems - stem thickness or girth increases in dicots due to secondary vascular tissue and periderm. The vascular bundles in the dicot stem are arranged in a ring. The activity of the cambium rings leads to the secondary shoot growth of dicotyledonous plants. The secondary growth of the dicot stem helps conduct water and nutrients and store food, and provides mechanical support to the stem.

Frequently asked questions about the secondary growth of dicot stems