Stages of Rooting Flashcards
Adventitious Roots
Form on a non-root tissue. Such as the stem or leaf petiole. Two types performed and wound-induced.
Aerial Roots
Are used in vines for climbing or in some tropical trees for extra support.
Anticlinal cell division
relating to the plane of a cell division perpendicular to the surface of a plant organ. In a cylindrical structure like a root or a stem ; when cell division occurs at the right angle to the length of an existing cell / s ; then it is ‘ Anticlinal division. It adds to the number of existing cells but their rows around that organ ( Root / Stem ) remain the same in number .
Brace roots
Formed in monocots at the base of stem to give extra support to the plant. Occurs in corn.
Callus
soft tissue that forms over a wounded or cut plant surface, leading to healing. A callus arises from cells of the cambium. When a callus forms, some of its cells may organize into growing points, some of which in turn give rise to roots while others produce stems and leaves. Thus a callus may be capable of regenerating an entire plant.
Cambium
In plants, a layer of actively dividing cells between xylem (fluid-conducting) and phloem (food-conducting) tissues that is responsible for the secondary growth of stems and roots, resulting in an increase in thickness. A cambium may also form within callus tissues.
Carbohydrate/Nitrogen ratio
Any of a group of organic compounds that includes sugars, starches, celluloses, and gums and serves as a major energy source in the diet of animals. These compounds are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, usually in the ratio 1:2:1.
Charles Hess
In 1959, Charles Hess detected “rooting cofactors” from extracts of the juvenile form of English ivy (Hedera helix).
Competent root forming cells
The ability to respond to rooting signal
Dedifferentiation/ differentiation
Dedifferentiation is a change that occurs in certain stem cells in response to wounding. It allows the change in the cell’s fate to form a new stem cell to a new root cell. The cell’s then divide and become meristematic. Differentiation in plants refers to the processes by which distinct cell types arise from precursor cells and become different from each other. Plants have about a dozen basic cell types that are required for everyday functioning and survival. Additional cell types are required for sexual reproduction.
Determination
When the fate of the cells has been made and these cells that were previously shoot cells are now becoming a new root cell.
Direct root formation
Direct root formation takes place from competent root forming cells present in the stem cutting.
These are usually phloem parenchyma cells that directly proceed to the four rooting stages. The usual pattern of rooting is for roots to form directly from cells in the phloem parenchyma.
They have a direct vascular connection with the main stem.
Indirect root formation
For difficult-to-root cuttings, rooting often follows an indirect pattern.
In this process, parenchyma cells must be induced to become competent to form roots. In the indirect pattern, root initials can not form directly near the vascular system. They form in callus that is induced in the cortex.
Periclinal cell division
when cell division occurs parallel to the length of the existing cell / s then it is ‘Periclinal Division ‘.
Polarity and rooting (proximal-distal)
Polarity is the condition inherent in a cutting that exhibits different properties in opposite parts.
Proximal is closest to the root-shoot junction.
Distal is away from the root-shoot junction. Stem cuttings form shoots at the distal end, and roots form at the proximal end. Root cuttings of many species form roots at the distal end and shoots at the proximal end. Cuttings at right were placed for rooting in an inverted position, but roots still developed from the proximal end.
Preformed root initials
Occur naturally on the stem while still attached to parent plant.
Root primordial
The earliest growth of root cells the first development of the cell.
Root bioassays
determination of the biological activity or potency of a substance, as a vitamin or hormone, by testing its effect on the growth of an organism.
Sclerenchyma ring and rooting
Serve as a support function in woody plants. The ring has said to hinder rooting but in most cases the root primordial can push right through the ring without complications and begin to form roots.
Stages of root formation
Stage 1- Dedifferentiation stage:
Dedifferentiation is a change that occurs in certain stem cells in response to wounding. It allows the change in the cell’s fate from a stem cell to a new root cell. Certain cells associated with the vascular bundle (usually phloem parenchyma cells) divide and become meristematic. The dividing cells that will become adventitious roots are densely cytoplasmic and have prominent nucleoli. The cell divisions are polar and the cells line up in parallel rows.
Stage 2- Root initial formation:
The second stage of root formation is the organization of dividing cells into a root initial.
A root meristem is starting to organize.
At this time, there is no evident vascular connection between the cutting and the new developing root.
Stage 3- Root primordial formation:
At this stage, the root primordia have organized a well defined root meristem and a root cap can usually be seen.
The vascular system of the root primordium is forming and reaching for a connection with the xylem and phloem in the parent stem. The root primordium has organized root meristem (M), a root cap (R) and vascular system (V) as it pushes through the cortex.
Stage 4- Root emergence:
The developing adventitious roots finally push through the cortex (C) and epidermis (E) and emerge to be functional roots.
There is a direct connection between the vascular systems (V) between the adventitious root and the cutting’s stem. For most softwood and herbaceous cuttings, the root emergence stage is complete between 20 and 30 days.
Wound-induced rooting
Develop only after the cutting is made, in response to wounding in preparing a cutting.
