stres fisiologi - temperatur stress (1).pdf
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STRES FISIOLOGI - Temperatur stress tumbuhanTRANSCRIPT
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DwiSetyati2013
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What is Plant Stress ?
Stress in biology is any change in
environmental conditions that might reduce
development.
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Stress Physiology
Resistance : resistance is the ability adaptive or tolerant to
stresses.
Resistance includes adaptation, avoidance and tolerance
Adaptation is permanent resistance to stress in morphology and
structure , physiology and biochemistry under long -term stress
condition.
a well -developed aerenchyma in hydrophytes,
a pattern for stomata movement in CAM plant .
Tolerance is a resistant reaction to reduce or repair injury with
morphology , structure, physiology , biochemistry or molecular
biology, when plant counters with stresses.
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Biotic stresspathogen microbe insectsAllelopathy
Abiotic stresschilling stress freezing stressheat stresswet stress flood stressdrought stress salt stress
temperatures stress
water stress
Biotic and abiotic stresses can reduce average
productivity by 65%~87%
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Crop Record
yield
Average
yield
Average losses Abiotic losses
(% of record
yield)
Biotic Abiotic
Corn 19300 4600 1952 12700 65.8
Wheat 14500 1880 726 11900 82.1
Soybean 7390 1610 666 5120 69.3
Sorghum 20100 2830 1051 16200 80.6
Oat 10600 1720 924 7960 75.1
Barley 11400 2050 765 8590 75.4
Potato 94100 28300 17775 50900 54.1
Sugar beet121000 42600 17100 61300 50.7
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chilling stress
freezing stress
heat stress
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Temperature stresses (high and low temperature)
are the major environmental factors affecting
plant growth, development and also induce
morphological, physiological and biochemical
changes in plants.
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Effects of high temperature stress on plants
It induces the changes in water relations (accumulation of
compatible osmolytes, decrease in photosynthesis,
hormonal changes and cell membrane thermostability
High temperatures stress (< 40"C) can cause :
- scorching of leaves and twigs,
- sunburns on leaves,
- branches and stems,
- leaf senescence and abscission,
- shoot and root growth inhibition,
- fruit discoloration and damage and reduced yield in
plants
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Formation of ROS is related to ethylene
production and lipid peroxidation and
results in membrane fluidity. Ethylene
overproduction has also been found during
or after recovery from water stress.
Leaf senescence and abscission
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Heat Stress
Berries are pink to bronze where directly exposed to
sun
Berries have a pleasant, wine smell
Occurs in extreme heat at/near harvest
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-Environmental stresses in plants have been
associated with production of activated forms of
oxygen , including hydrogen peroxide (H 2O2),
singlet oxygen, superoxide, and the hydroxyl
radical . Through a variety of reactions, O 2*-leads
to the formation of H 2O2, OH* and other ROS.
- Reactive oxygen species (ROS) are produced
continuously as by products of different metabolic
pathways which are located in different cellular
compartments such as chloroplast, mitochondria
and peroxisomes.
HEAT TEMPERATURE STRESS
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- The ROS comprising O2*-, H2O2, 1O
2, HO2*-, OH*,
ROOH, ROO+ and RO+ are highly reactive and toxic
and causes damage to proteins, lipids, carbohydrates
and DNA which ultimately results in cell death.
Accumulation of ROS as a result of high temperature
stress is a major cause of loss of crop productivity
worldwide.
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HEAT TEMPERATURE STRESS
-induces the rapid production and accumulation of reactive
oxygen species (ROS) (Mittler, 2002 Xu et al. 2008).
- These high levels of ROS are harmful to all cellular compounds
and negatively influence cellular metabolic processes
(Breusegemet al.,2001).
- The detoxification of these ROS is very important and plants
have evolved complex strategies to deal with them (Asthir et al.,
2009).
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High temperature stress in Sugarcanecauses a severe
reduction :
- in the first internodelength resulting in premature
death of plants.
- exhibited smaller internodes,
- early senescence,
- and reduced total biomass
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The plant life cycle both vegetative and reproductive phases
are affected by the low temperature stress (Nishiyama, 1995).
During reproductive development low temperature stress :
- induces flower abscission,
- pollen sterility,
- pollen tube distortion,
- ovule abortion and reduced fruit set, which ultimately
lowers yield.
During the reproductive phase cold stress has important
economic and social consequences because the reproductive
phase products are the key components of economic yield and
are the principle source of food for entire humanity (Thakuret
al, 2010).
LOW/COLD TEMPERATURE
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The reproductive phase begins with transformation of the
meristeminto inflorescence and flower and, in annuals, ends
upon seed reaching maturity.
The reproductive phase consists of :
- flower initiation,
- differentiation of male and female floral parts,
- micro- and mega-sporogenesis,
- development of male and female gametophytes
(pollen grain and embryo sac),
- pollination,
- micro- and mega-gametogenesis,
- fertilization and seed development.
All these stages respond differently to cold stress but
collectively all responses are negative and reduce net yield.
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Freezing injury
is caused by low
temp.
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Intercellular crystallization
Ice crystals form between cells.
Intracellular crystallization
Ice crystals form in the cell.