Open growth : It is a type of growth where in new cells are always being added to the plant body by the activity of the meristem.
Growth is considered to be open. Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. The meristems present in different locations have the capacity to divide and self-perpetuate. The daughter cells may lose the capacity to divide and such cells make up the plant body. ns in which they are formed.
Diagrammatic representation of locations of root apical meristem, shoot apical meristem and vascular cambium. Arrows exhibit the direction of growth of cells and organ
Differentiation in plants is open, because cells/tissues arising out of the same meristem have different structures at maturity. The location also decides the final
structure of a cell/tissue at maturity. For example, cells positioned away from root apical
meristems differentiate as root-cap cells, while those pushed to the periphery mature as epidermis.
Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.
Auxins are of two types :
(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.
(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.