2. Stress : Environmental damage to plants
◇ Biotic stress Abiotic stress◇
Resistance : The adaptability of plants to adverse environment
◇Stress avoidance Stress tolerance◇
Stress Physiology : adversity makes an impact on plant life
activities, resistance of plants to adversities
4. TypesTypes ooff ResistanceResistance
stress avoidance
In the whole growth process does not meet with the face of
adversity
stress tolerance
Plant has a capacity of environmental stress defense, and a variety
of physiological processes remain normal
6. Cold stress: complex!
Plants can be damaged in different ways by:
Low day/night air temps
Low day/night soil temps
Differences in plant tissue sensitivity.
Species differ in their sensitivity to temp., depending on
their origin:
Cool-season
Warm-season
7. Damage from cold
Depends on many factors:
1. Developmental stage
2. Duration/severity of frost
3. Rates of cooling, rewarming
4. Ice formation:
Intracellular: disintegrate cell membrane.
Extracellular in intercellular spaces.
8. Low temperature stress
Effects of low temperature
Dehydration of cells/tissues when cellular water freezes
Beck et al. 2004
9. Cold acclimation
Acclimation involves
Synthesis of cryoprotectant molecules such as:
o Soluble sugars
o Sugar alcohols
o Low molecular weight nitrogenous compounds.
– Upregulation of genes for
» Dehydrins
» Cold regulated proteins (COR)
» HSPs
Janska et al. 2010
10. They are stress proteins with a high number of charged amino acids that
belong to the Group II Late Embryogenesis Abundant (LEA) family”. DHNs are
primarily found in the cytoplasm and nucleus but more recently, they have
been found in other organelles, like mitochondria and chloroplasts. DHNs are
characterized by the presence of Glycine and other polar amino acids. All
DHNs contain at least one copy of a consensus 15-amino acid sequence. The
“K segment, The K segment is a Lysine-rich 15-amino acid consensus
sequence (EKKGIMDKIKEKPLG) that is highly conserved in all plants”
Dehydrins
11. COLD ACCLIMATION
Synthesis of cryoprotectant
molecules
Soluble sugars
Sugar alcohols
Low molecular weight
nitrogenous compounds
Upregulation of genes for
Dehydrins
Cold regulated
proteins (COR)
HSPs
Janska et al. 2010
12. Contd...
Change in membrane lipid composition.
Suppression of phospholipase D.
Synthesis of antifreeze proteins.
An altered ratio of ABA to GA.
Janska et al. 2010
15. Enzymatic and metabolic responses
Upregulation of galactinol synthase
Induction of SPS gene
Upregulation of proline synthesis
Upregulation of Glutamate decarboxylase genes
Suppression of lipid metabolism
Increase in biosynthesis of anthocyanins and flavonoids
Janska et al. 2010
16. ENZYMATIC AND
METABOLIC RESPONSES
Induction of
SPS gene
Upregulation
of
galactinol
synthase
Increase in
Anthocyanins
and
flavonoids
Upregulation
of
proline synthesis
Upregulation
of
GAD genes
Suppression
of
lipid metabolism
Janska et al. 2010
18. Cold sensing and signaling
Potential sensors include
Ca2+
influx channels
Two component histidine kinase
Receptors associated with G-proteins
Change in cytoskeletal elements
Plasma membrane rigidity
Janska et al. 2010
19. Fig: Scheme illustrating the molecular response of plants to low-temperature stress,
realised as changes in transcriptome, proteome, metabolome and phenotype.
Janska et al. 2010