Data di Pubblicazione:
2006
Citazione:
Fisiologia postraccolta dei fiori recisi / A. Ferrante, M.S. Reid. - In: ITALUS HORTUS. - ISSN 1127-3496. - 13:4(2006), pp. 29-41.
Abstract:
The study of the postharvest physiology
of cut flowers has the aim of understanding the behaviour
and disorders of harvested flowers. The dramatic
differences between the conditions in the growing
environment and in the storage facility affect the physiology
of cut flowers. Understanding the biological
mechanisms that are activated or inhibited during storage
is essential to developing technical strategies for
avoiding quality losses. External quality (appearance)
is extremely important to the consumer. Although consumer
choice is driven by external quality, the
postharvest life, or vase life, is key to convincing the
consumer to re-purchase cut flowers. Postharvest
physiology therefore has a double goal: to preserve
external quality during the distribution chain and to
extend the vase life of the flowers. The key to extending
flower life after harvest is understanding the biological
processes governing postharvest physiology:
respiration, ethylene production, water loss (transpiration),
hormonal imbalance and the activation of enzymes
associated with flower discoloration and leaf yellowing
(chlorophyll loss). Respiration is the fundamental
metabolic process responsible for providing energy
in all living cells. During postharvest life, cut flowers
depend on stored reserves (starch and sugars) for
respiration. Because flowers are poikilotherms, the
rate of respiration is dependent on temperature,
increasing in an exponential fashion with increasing
temperature. For cut flowers, the Q1 0 (the ratio of
respiration at temperature T to that at temperature T-
10) is usually at least 3, and may be as high as 9.
This means that respiration (and deterioration) at 20 C
is at least 9 times more rapid than at 0 C; rapid cooling
and maintenance of temperature is therefore key
to maintaining the vase life of harvested flowers.
After harvest, the hormone equilibrium in cut
flowers is frequently altered. Stress conditions stimulate
ethylene biosynthesis, which leads to rapid senescence
or abscission in ethylene-sensitive cut flowers.
The physiological effects of ethylene are expressed
when tissues are sensitive to this plant hormone,
which requires the presence in the cells of ethylene
receptors. Plant ethylene receptors have been studied
in model systems (principally Arabidopsis thaliana)
and, although much is now known of their structure
and function, new details are continually being discovered.
Cut flowers that are sensitive to ethylene
respond fully to concentrations of 1 to 3 μL L- 1, and
last longer when treated after harvest with inhibitors of
ethylene biosynthesis or action. Abscisic acid (ABA) is
another plant hormone that can play an important role
during flower senescence. ABA accumulation is induced
in leaves and petals by water stress, and may
result from carotenoid degradation in leaves.
Increased ABA concentrations may trigger flower
senescence in some species.
Once harvested, flowers no longer receive cytokinins
from the roots of the mother plant. The lack of
these hormones results in the induction of leaf yellowing.
Exogenous treatment with natural cytokinins
or substituted phenyl-ureas with cytokinin-like activity
can inhibit chlorophyll degradation and leaf yellowing.
Excessive water loss frequently compromises the
storage and vase life of harvested cut flowers.
Continued transpiration in detached flowers leads to
water imbalance, resulting in flower wilting. To avoid
excessive water losses, cut flowers should be cooled
immediately after harvest.
Storage and transportation conditions strongly
affect cut flower physiology and subsequent vase life.
The environmental factors that directly affect cut
flower physiology are temperature, relative humidity,
exoge
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
quality; storage; ethylene; respiration;
temperature
Elenco autori:
A. Ferrante, M.S. Reid
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