MindMap Gallery Plant roots mind map
The mind map of plant roots includes the primary growth and primary structure of roots, root functions, secondary growth and secondary structure of roots, etc.
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plant roots
root shape
Definite roots (tap roots and lateral roots)
Lateral roots originate from pericycle cells
Adventitious roots
Primary growth and primary structure of roots
apical partition
root crown area
Located at the forefront of the root tip, it is composed of thin-walled cells. It is a unique structure of land plants and contains balance stones.
meristematic zone
Located inside the root cap, also known as the growth point, it is the place where new cells are produced. It is the apical meristem of the root. The cells are small, the cytoplasm is dense, the cells are tightly arranged, there are no intercellular spaces, and the nuclear-to-cytoplasmic ratio is large.
protomeristem (quiescent center)
primary meristem
elongation zone
Mature area
The appearance of root hairs on the root surface is an external sign of the transition from the elongation zone to the mature zone of the plant.
primary structure of root
Primary structure of dicotyledonous plants
epidermis
Located at the outermost side of the mature area, it is formed by the original epidermis and has no stomata. The outer tangential walls of some epidermal cells protrude outward to form root hairs to expand the absorption area.
cortex
Developed from basic meristems and responsible for the lateral transport of water and inorganic salts into the pericycle
outer cortex
The cell walls of the outer cortex cells are often thickened and lignified, becoming a structure that replaces the epidermis.
The main reason for the loss of root hairs is the suberization of the outer cortex cells on the inside.
cortical parenchyma cells
endothelium
There are band-like thickened areas of lignification and suberization (Kjeldahl bands) on the upper and lower transverse and radial walls of endothelial cells.
The Kjeldahl band blocks the apoplast pathway of water and inorganic salts in the root, playing a selective permeability role.
center column
pericycle
Located in the outermost layer of the pericycle, it is composed of a layer of thin-walled cells with low differentiation.
Lateral roots, adventitious roots, adventitious buds, cork cambium, and part of the vascular cambium are all produced by pericycle cells restoring their ability to divide.
primary xylem
The procambium develops and matures centripetally from outside to inside (exogenous type). The first one to be produced is called protoxylem, and the later one is called metaxylem.
The radiating edges of primary xylem are called xylem bundles (ridges). Monocots are generally >6 and dicots are generally <6.
primary phloem
Its development mode is also exogenous, with primary phloem on the outside and epiphloem on the inside.
basic organization
Located between primary xylem and primary phloem, in the center of dicotyledonous plant roots, generally without pith
Primary structure of monocots
epidermis
often disintegrates and falls off
cortex
outer cortex
In the later stages of development, the outer cortex often transforms into suberized thick-walled tissue, which replaces the epidermis and plays a protective role after the epidermis and root hairs fall off.
cortical parenchyma cells
Form air cavities (e.g. aquatic plants)
endothelium
Except that the tangential wall is often thickened on five sides and has channel cells.
center column
No parenchyma cells, usually myelinated
occurrence of lateral roots
The occurrence of lateral root primordium
Originates from inside the plant (endogenesis)
formation of lateral roots
A few adventitious roots occur in the epidermis and subepidermal cortical cells (external origin)
root function
Absorption and conduction (mainly relying on root hairs and young epidermal cells at the root tip)
Fixation and support
Storage and reproduction
synthesis
Secretion
Secondary growth and secondary structure of roots
The occurrence and activities of the vascular cambium
The occurrence of vascular cambium
It occurs in the root tip mature zone and is a circular structure formed by the basic tissue in the pericycle and the pericycle cells facing the primary xylem bundle, which restore their ability to divide.
vascular cambium component cells
cell composition morphology
spindle primitive cells, ray primitive cells
cell division mode
Divide at the periphery to produce secondary vascular tissue and thicken the root
Spindle cells divide radially and perpendicularly, increasing the circumference of the vascular cambium to accommodate root thickening.
vascular cambium activity
After the vascular cambium cells divide periperitically, the inner daughter cells form secondary xylem and are added to the outside of the primary xylem, and the outer cells form secondary phloem and are added to the inside of the primary phloem. The proportion of secondary xylem is greater than that of secondary phloem
The occurrence and activity of cork cambium
The cork cambium formed by the recovery of division ability of pericycle cells is also called primary cork cambium. The cork cambium formed by cells other than pericycle cells that resume division ability is called secondary cork cambium. The cork cambium, cork layer, and cork inner layer together constitute the secondary protective tissue of the root—periderm.
The tissue composed of horizontally arranged parenchyma cells is called rays. Those located in secondary xylem are called wood rays, and those in secondary phloem are called phloem rays.