JUVENALITY IN FRUIT PLANTS
In the development of all woody plants from seed
there is a juvenile phase lasting up to 3 to 4 years or even more,
during which flowering does not occur and cannot be induced by the normal
flower initiating treatments (application of growth regulators) or conditions (water stress). After completion vegetative or juvenile phase of the plant it will proceeds
towards the reproductive phase. At this stage, the tree is considered to have
attained the adult or sexually mature condition. The length of the juvenile
period can be influenced by environmental as well as genetic factors.
The organs and tissues
produced by a young plant, such as a seedling, are often different from
those that are produced by the same plant when it is older. This phenomenon is
known as juvenality or heteroblasty. For example, young
trees will produce longer and thinner branches that grow upright than the
branches they will produce as a fully grown tree. In addition, leaves produced
during early growth tend to be larger, thinner, and more irregular than leaves
on the adult plant. Specimens of juvenile plants may look so completely
different from adult plants of the same species.
Juvenile cuttings taken from
the base of a tree will form roots much more readily than cuttings originating
from the mid to upper crown. Flowering close to the base of a tree is absent or
less profuse than flowering in the higher branches especially when a young tree
first reaches flowering age. When we take the different propagating materials
like cutting, budding, grafting etc from one juvenile plant they will bear
flower late and in fully established plant it will be quicker.
During its life cycle the plant undergoes embryonic,
juvenile, transitional (between juvenile and mature), and mature (adult) phases
of growth and development followed by senescence and death. The juvenile phase
in some species has a distinctive morphology of leaves, stems, and other
structures which are no longer present when the plant becomes mature. Once the
plant reaches maturity, flowering can be induced by appropriate external agents
like growth regulators, bahar treatments etc. The change from mature to
senescent conditions typically involves the deterioration of many synthetic
reactions leading to the death of the plant, thereby completing the cycle.
Juvenility
is defined strictly in terms of ability of seedlings to form flowers. The
juvenile phase ends with the attainment of the ability to flower. The
appearance of the first flowers on the seedling is the first evidence that the
plant is in the adult phase. Any transition period between the 2 phases is
qualitatively the same as the adult phase, but there is presently no method for
distinguishing such a transition period from the juvenile phase.
Seedlings
which have responded to growth retardant treatments by flowering at an earlier
age are considered to have been in a transition period at the time they were
treated.
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