Senescence refers to the deterioration of plants with age and the final stages of life. There are several types of senescence like top, deciduous, overall, and progressive senescence. Retarding senescence can delay degradation and increase plant life and yields. Several factors can retard senescence including plant hormones like cytokinins and auxins, nutrients like calcium and nitrogen, temperature, and light exposure. Experiments show that auto-regulated production of cytokinin, ascorbic acid, polyamines, and inhibitors of RNA and protein synthesis can effectively retard leaf senescence in plants. Subtoxic levels of photosynthesis inhibitors like bromacil and atrazine also retard senescence in ma

1. Senescence it’s
Retardation of Senescence

2. Senescence
Life comprises of following sequential events
germination/birth, juvenile state, maturation, old
age and death.
Old age called senescence in plants.
Senescence biological process of deterioration
with age.
This stage leads to complete loss of organization
and function and finally complete inhibition of life
activity i.e. death, thus senescence is penultimate
phase of life. But death is not part of senescence.
Meristem don’t undergo senescence and are
considred as potetially immortal.

3. Types of senescence
Top senescence :- occurs in aerial
parts of plant. Common in perennials.
Deciduous senescence :- Occurs in
deciduous plants. Only occurs in
leaves.
Overall senescence :- seen in annual
plants. Senescence occurs orderly in
flower, fruits, leaves and root.
Progressive senescence :- It is
common in annual plants. First seen
on old leaves and then new leaves.

4. Retardation of senescence
It means that delay the degradation of
plant.
Also increase the life of plant and
getting more and more yield.
Delay the senescence of many plant
parts i.e. flowers, leaves and fruits.
This retardation of senescence with
the help of many factor studied by
many people these are as follows:

5. Inhibition of Leaf Senescence by
Auto regulated Production of
Cytokinin.
Controlling expression of IPT, a gene
encoding isopentenyl transferase (the
enzyme that catalyzes the rate-limiting step
in cytokinin biosynthesis), with a senescence-
specific promoter results in the suppression
of leaf senescence.
Transgenic tobacco plants expressing this
chimeric gene do not exhibit the
developmental abnormalities usually
associated with IPT expression because the
system is autoregulatory. Because sufficient
cytokinin is produced to retard senescence,
the activity of the senescence-specific
promoter is attenuated.

6. Senescence-retarded leaves exhibit a
prolonged, photosynthetically active
life-span. This result demonstrates
that endogenously produced cytokinin
can regulate senescence and provides
a system to specifically manipulate the
senescence program.

7. Retardation of Leaf Senescence by
Ascorbic Acid
Leaf discs of Solatium melongena were
floated on various concentrations of
ascorbic acid (AA), gibberellic acid
(GA3), and kinetin in order to study their
effect on senescence.
 AA was highly effective in retarding
senescence as shown by the arrest of
the fall in levels of chlorophyll, DNA,
RNA, and proteins.
 AA was effective at a lower
concentration than that of GA3 or kinetin.

8. Retardation of leaf senescence by
inhibitors of RNA and protein
synthesis
 Effects of actinomycin-D (ACT), cycloheximide
(CH), rifampicin (RIF) and chloramphenicol
(CAP) on senescence of soybean leaf discs were
investigated.
 All inhibitors tested are effective in retarding
senescence of soybean leaf discs. However, CH
is more effective than ACT, RIF and CAP,
suggesting that activation of preexisting, latent
metabolic systems present in the cytoplasm
plays predominant role in the initiating of leaf
senescence.
 However, the possibility that events taking place
in the nucleus or chloroplast are essential for the
initiation of leaf senescence cannot be excluded.

9. Retardation of radish leaf
senescence by polyamines.
 The effect of polyamines and related metabolites on
several parameters of leaf senescence was followed
in detached radish (Raphanus sativus L. var.
radicular cv. “Giant Butter”) leaves floated on test
solutions in darkness.
 Leaf senescence was accompanied by a marked
loss of chlorophyll, which started at 24–48 h of
incubation. The polyamines, spermine and
spermidine, and the diamines, putrescine and
cadaverine, were highly effective in arresting
chlorophyll loss over a period of at least 96 h. L-
arginine, and especially L-ornithine, were less
active. Polyaminens prevented the marked
chlorophyll loss in dark-incubated leaves, but did not
compensate for the moderate chlorophyll loss when
the leaves were aged in light.

10. Polyamines were also highly effective
in retarding earlier events of leaf
senescence, prior to chlorophyll loss:
both protein degradation and
ribonuclease activity were inhibited by
spermidine.

11. Chlorophyll and protein loss in dark-or
light-incubated suspensions of either
“intact” or disrupted chloroplasts was not
affected by polyamines. – It is concluded
that polyamines are highly effective in
preventing chlorophyll loss from detached
leaves, possibly by controlling early
senescence-linked events which occur in
darkness rather than by direct inhibition of
chlorophyll degradation.

12. Retardation of senescence by low
temperature and benzyladenine(BA)
in intact primary leaves of soybean.
Effects of temperature and
benzyladenine (BA) on the
senescence of intact primary leaves
of soybean were investigated.
Compared with high temperature
(30°C for day and 25°C for night),
low temperature (15°C for day and
13°C for night) significantly retarded
senescence of intact primary leaves.

13. Repeated daily treatment of the
primary leaves with BA (200 mg/liter)
beginning 15 days after growth at high
temperature resulted in retardation of
the senescence process.
The lower activity of cytokinins in the
primary leaves of seedlings grown
under high temperature may be
responsible for rapid senescence.

14. Retardation of Leaf Senescence in Maize
by Subtoxic Levels of Bromacil,
Fluometuron, and Atrazine
Soil applications of subtoxic dosages of
three selected photosynthesis inhibitors
caused marked retardation of senescence
in the basal leaves of maize (Zea mays L,
cultivar Cribfiller)
The observations were confirmed
quantitatively by (a) spectrophotometric
determination of relative chlorophyll
content and (b) comparison of 14CO2
incorporation, in leaves from treated and
control plants.

15. Bromacil (5-bromo-3-sec-butyl-6-
methyluracil) and fluometuron (1,1-
dimethyl-3-(α,α,$a lpha$-trifluoro-m-tolyl)
urea) exhibited pronounced activity, by
both criteria, retarding senescence at 0.
030-0.090 ppmw and 0 150-0.750 ppmw
in the soil, respectively.
 Atrazine (2-chloro-4-(ethylamino)-6-
(isopropylamino)-s-triazine) produced a
similar trend but at higher concentrations
(0.300-0 900 ppmw).

16. The results obtained with bromacil and
atrazine add to the literature two new
chemical classes of compounds (uracils
and triazines) which contain no purine ring
yet exhibit one recognized cytokinin-like
activity, retardation of senescence in intact
plants.

17. From above discussed experiments we
concluded that there are many factors
responsible for retardation of senescence.
Mainly due to more secretion of cytokinin,
auxin, GA3, polyamines and other growth
retardent are retarded the senescence.
We all known about the Richmond-Lang
Effect due to available of cytokinin.

18. Factors responsible for
retardation of senescence.
Plant harmones :- Auxin, cytokinin,
GA3, polyamines and other growth
retardents.
Types of nutrients :- Calcium and
Nitrogen application.
Availability of water/ irrigation.
Light :- opening of stomata in light
time.
Temperture :- lower temp. Retard
senescence.

19. Case study

20. Conclusion

21. References
Plant Physiology - S. N. Pandey and
B. K.Sinha
Text book of Biology – Vaishali patil-
Shirure
Journal of Plant Cell Physiology
Journal Exp. Botany
Internet Wikipedia page

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