Biochemistry of Flower Senescence - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 76

plants. In concert, these changes gave a dramatic effect: the flower longevity was prolonged
with approximately 100% in nonpollinated flowers and approximately 450% in pollinated
flowers.
4.17 Breeding/genetic modification to improve postharvest quality
To date, use of gene transfer technology to delay flower senescence has highlighted the need
for tightly regulated transgene expression to avoid affecting other nontarget developmental
processes, particularly in the modification of plant hormone levels (e.g., poor rooting and
lower disease resistance in ethylene-insensitive plants) (Clark et al., 1999; Shaw et al.,
2002). Thus, the need for tissue-specific promoters is paramount for exploiting this avenue
of crop development in commercially important cultivars. Alternatively, modifying the
expression of metabolic genes may produce satisfactory postharvest improvements without
the need to alter hormone biosynthesis or perception, which may have pleiotrophic effects.
Pollen sterility in flowers innately lowers pollen-induced senescence signals, and may make
currently unsuitable flowers suitable for cut flower cropping without needing antiethylene
treatments. The use of traditional breeding to select for genetic improvement of vase life
may progress more rapidly as genetic markers for “long life” are identified and as gene
transfer technologies provide a way to improve the postharvest characteristics of crops with
low genetic diversity.
4.18 Future perspectives
There is little doubt that the molecular and genetic analyses of flower senescence made in
the past 5 years have raised our awareness of the complex interactions that occur to regulate
flower development and senescence. Genetic technologies have enabled scientists to search
for senescence-related genes in plants often described as science models (e.g., Petunia ,
Arabidopsis ), and then translate the data into other species to determine the functional
significance of the expression of specific genes in specific tissues after harvest. Interactions
between ethylene, cytokinin, sugars, and various hydrolytic enzymes are now known to
differentially mediate the progression of flower senescence. The individual importance of
each signal appears to be species specific and, in some instances, variety specific, and varies
differentially between floral organs. The challenge for postharvest scientists is to identify a
hierarchy of regulators or a specific pattern of events that progresses senescence for certain
groups of flower species. Subsequent categorization of cut flowers based on their metabolism
and sensitivities will enable targeted application of appropriate postharvest technologies.
References
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