(i) Juvenile phase
(ii) Reproductive phase
(iii) Senescent phase
(i) Juvenile phase is the period of growth between the birth of an individual up to maturity.
(ii) Reproductive phase starts after the juvenile phase and remains up to the stage when an organism is capable of reproduction.
(iii) Senescent phase is the phase of ageing when an organism loses its capacity of reproduction. In plants, it is characterised by yellowing and leaf fall.