Agriculture Reference
In-Depth Information
bearing and to guarantee good yield quantity and fruit quality. The yield is strictly
dependent upon the carbon source and the energy metabolism basically generated
by the canopy, resulting from the vegetative activity of the tree. Since excessive
shooting may negatively affect fruit bud differentiation and fruit development, the
vegetation should be finely controlled to achieve the proper balance between veg-
etative and reproductive activities. On the contrary, an excessive fruit load may be
detrimental for an inadequate canopy development, for current year fruit quality
and for flower bud differentiation. The criteria to achieve a vegetative/reproductive
balance are quite complex and depends primarily upon rootstocks and cultivars. For
example, the use of standard or spur/compact type cultivars may require complete-
ly different management approaches to achieve best results in terms of cropping.
The maturity is the longest phase of the tree life cycle and the most important for
the economic return of the orchard.
Senescence
Senescence is the last phase of the plant life cycle. It is a physiological syndrome
that in monocarpic species becomes established in the plant very early during the
transition phase, long before the differentiation of flower structures. In this case, the
term used is “overall senescence” because all the plant body dies with the excep-
tion of the seeds which are in turn responsible of the species survival. In the case of
polycarpic species, senescence is not related to transition phase but is regulated by
different mechanisms changing according to the type of organ undergoing senes-
cence. In the case of fruit trees species, the term “deciduous senescence” is adopted.
The syndrome occurs at the end of each growing season and affects only leaves and
fruits while the tree woody structure is maintained trough years. Organs undergo-
ing shading are usually depleted of the plastic substances which are mobilized to
and accumulated in storage parenchyma, and used to support the tree phenology
in the following spring. The total senescence concludes the tree life cycle also in
fruit trees, as a results of a process of aging that affect all the tree body. At the end
of the adult phase, the tree slowly enters the senescence phase. The syndrome is
established slowly and progressively manifested by reduction of meristem activity
leading to a reduced number of phytomers, a slowdown of growth potential and an
increase of the ratio between short and long shoots.
The Biology of a Fruit Tree
The Adult Vegetative Phase
Although orchards are made up of trees in adult phase, flower bud differentiation
remains an alternative developmental path occurring only under proper external
