Juvenileplants are not able to
produce flowers; they are
capable of only
vegetative growth. As a consequence the capability to
reproduce is a sign of
the transition from the
juvenile phase to
adulthood.
Juvenile plants often differ in appearance from the adult ( See:
primary
and
secondary sexual characteristic). Juvenile
tissues are produced first,
near the base of the plant.
The adult phase is
usually stable and can be
propagated
from plant to plant.
Differently a mature plant
can flower and is said to be "ripe-to-respond (or flower)"
or "competent".
That is, it has the potential to flower when the conditions are
suitable. The process of flowering depend upon a complex
ensemble of environmental
factors (e.g. photoperiod,
temperature,
water availability, etc.)
internal factors (e.g.
hormon balance,
nutrient levels,
health,
age, etc.) with correlative
influences from various organs
(e.g. mechanism that to insure that there is a sufficient
vegetative mass and
storedreservoir to
support the reproductive
output).
Floral induction may be
completed by plants in several alternative sets of environmental
factors. At least in some plants, the alternative inductive
factors are perceived by different
organs, indicating that these
factors affect most probably entirely different
processes. Thus the
shootmeristem appears to be
controlled by a complex and flexible array of
promoters and
inhibitors arising from
all plant parts. At meristem
evocation, there are a number of events which are
fundamentally the same in many plants, but so far no single
initial critical event has been found.
The transition from the
vegetative to
reproductivebuds is usually activated
by an environmentalsignal, typically
photoperiod or
temperature. This
signalsynchronizes
flowering to environmental events that plants use to coordinate
actions with the season.
In some plants, an environmental signal is not necessary to
activate the transition to the determined state. These plants
move directly in the reproductive phase after becoming
competent.
Ultimately, one or more of these factors likely induce changes
in hormones such as
GA (Gibberellic acid);
for example GA application
stimulates the adult phase in conifers but in ivy promotes
juvenility
Some species of climbing
plants develop holdfast roots which help to support the vines on
trees, walls, and rocks. By forcing their way into minute pores and
crevices, they hold the plant firmly in place.
Climbing plants, like the poison ivy (Toxicodendron
radicans), Boston ivy (Parthenocissus
tricuspidata), and trumpet creeper (Campsis
radicans), develop holdfast roots which help to
support the vines on trees, walls, and rocks. By forcing their
way into minute pores and crevices, they hold the plant firmly
in place. Usually the Holdfast roots die at the end of the first
season, but in some species they are perennial. In the tropics
some of the large climbing plants have hold-fast roots by which
they attach themselves, and long, cord-like roots that extend
downward through the air and may lengthen and branch for several
years until they strike the soil and become absorbent roots.
Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House,
1994
