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 The Main Parts and Functions of the Carrot Root


The purpose of a root is to anchor the plant to the ground and to absorb water and nutrients - diagrams below.

Examples of typical carrot root shapes here.  More detail on root structure and formation here. (Biology web - Carrots are didcots)

The root normally comprises 6 elements:

The root cap

Conical covering of the tip of the root which covers the apical meristem (undifferentiated cells). It protects against scratches while moving through the soil and excretes a mucus like substance called mucigel that allows the root to move through the soil easily.


Epidermis (skin)

Is the hard outer layer on a root absorbing water from surrounding soil through osmosis
Produces root hairs

Also known as the Peel, or periderm - Roots take water from the capillary spaces between soil particles. This function is carried out by the young portions of the roots at the location of minimal cutinisation of the epidermis and at maximum surface area. This location is found in the root-hair zone just proximal from the growing root tip. Thus roots take in their water through very fine roots located at the drip-line of the plant's canopy.


Root hairs

These are small, microscopic hairs on the outside of the epidermis and serve to increase the surface area of the root. They only survive for only a few days

The Cortex

Is located below the epidermis. Makes up the bulk of the primary root. Main purpose is to store starches. The sugar and carotene are contained in the Cortex.

The Cortex is comprised of the phloem, or nutrient conducting tissue - phloem conducts photosynthate from the leaves to the root tips. The metabolism of roots growing in the dark of the soil is essentially dependent upon respiration. This process requires carbohydrate or other organic molecules as fuel. It also requires a supply of oxygen, which is why soil needs to drain well for good plant growth.)

Endodermis

This is the thin layer of cells in the center of the cortex surrounding the xylem and phloem . It forces minerals into the xylem and phloem

Central Core

The Central Core comprised of xylem (a water conducting tissue, transporting water from root to leaf) All Roots contain xylem to conduct water from the soil up the plant and out through the leaves. These xylem tracheids and/or vessels are connected to others in an end-to-end design allowing soil water and minerals to be lifted up to the leaves. The evaporation of water from the leaves is the major pull of water through the xylem, but roots can also develop "root pressure" osmotically when the soil is well-watered and the plant has sufficient reserves.
 


 

In the US Department of Agriculture circular dated March 1950 are listed 389 names that have been applied to orange-fleshed carrot varieties or strains. This gave a thorough classification of all varieties of orange rooted carrots found in the US at the time.

On the basis of their general or outstanding characteristics these varieties or strains were classified in 9 major groups, as follows:

I, French Forcing; II, Scarlet Horn ; III, Oxheart ; IV, Chantenay ; V, Danvers ; VI, Imperator; VII, James' Intermediate; VIII, Long Orange; and IX, Nantes.

(Source -Synonymy of Orange-Fleshed Varieties of Carrots M F  Babb 1950).

Right shows the longitudinal section of a carrot illustrating the terms used in the circular for varietal descriptions.

For information here is the full classification of a carrot:

Kingdom Plantae – Plants
Subkingdom Tracheobionta – Vascular plants
Superdivision Spermatophyta – Seed plants
Division Magnoliophyta – Flowering plants
Class Magnoliopsida – Dicotyledons

Subclass Rosidae
Order Apiales
Family Apiaceae – Carrot family
Genus Daucus L. – wild carrot P
Species Daucus carota L. ssp. sativus- domestic carrot

(It is generally accepted that carrot is drawn from the wild variety)

Note - Some classifications show Umbelliferae rather than Apiaceae


Important Note - The chemical constituents of carrot are not there by chance, but perform a function. Many constituents of the orange carrot we now cultivate are also in the white root of the wild carrot, Queen Anne's lace, from which our carrot was developed. This is true of falcarinol, falcarindiol, and myristicin. Carotene (present in small amounts in Queen Anne's lace) has been increased by centuries of selection. Volatile oils have been decreased in this process. Plant scientists must continue to monitor all known constituents nutritive and non-nutritive - as new cultivars of the carrot are developed to keep our vegetables nutritious and safe. Plant breeding for the sake of high yields, appearance, and keeping quality will not be sufficient.

Carotenoid pigments provide red, yellow and orange colours and antioxidant protection to a wide variety of plants, animals, bacteria, and fungi. In plants, carotenoids play a protective role in photosynthesis by dissipating excess light energy absorbed by the photosynthetic mechanism. 

What it means is that carotenoids are good antioxidant compounds which effectively prevent damage to DNA or other important parts of cells. This damage can be caused by ‘free radicals’ which are very reactive molecules generated through the normal living processes of a cell (the release or generation of energy).

In plants, the carotenoids protect the plant cells from damage caused by energy from the sun in the same way. Carotenoids are also a starting point for the construction of other useful compounds, so their function is not always protective. There are possibly more important  parts of the plant containing carotenoids (eg the leaves) where they are less obvious because they are masked by the green colour of chlorophyll. In the parts of the plant which don’t photosynthesize, we can see their presence more easily.

 

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