EG 9&10 Flashcards
where do abiotic stresses come from and some examples
result from environmental factors unrelated to living organisms
eg. drought, waterlogging, temperature, ozone, salinity, UV, oxygen levels
where do biotic stresses come from
result from the activity of other living organisms
how do plants pick up on environmental cues
plant genomes encode sensors and signal transduction pathways that monitor and trigger response to environmental cues
-control nutrient and water transport, energy production, storage to improve survival
what is adaptation and examples
genetic changes over many generations due to stress or specific environment
eg. deep roots, protected stomata, reflective spines
what is acclimation and example
temporary response to a specific stress, no genetic changes so typically reversible
eg. water deficient crop will display reduced growth as it is putting its energy into survival and water storage not growth
how is water deficiency detected in plants
plasma membrane localized pressure sensors sense changes in pressure or turgor in the cell
what is ABA
abscisic acid, essential plant hormone for regulating developmental processes (seed maturation) and stress responses (dessication tolerance - drought)
what is the ABA biosynthesis workflow
first step of ABA biosynthesis occur in chloroplast, 1 intermediate (xanthoxin) moves into cytosol, ABA can be inactivated by oxidation or conjugation
what is the ABA signalling pathway workflow
-relies on phosphorylation
different components are:
-ABA receptors
-a kinase (phosphorylates the transcription factors that will activate ABA-responsive genes)
-a phosphatase (interacts with ABA receptors)
-transcription factors (activate ABA-responsive genes)
why and how do stomata close
-ABA plays important role in triggering the closure of stomata
-stomata close in response to a threshold of soil moisture meaning drought causes stomata to close
-stomatal closure affects transpiration and gas exchange of plants
what is waterlogging vs submergence and their effect
when the soil is saturated with water vs. when soil is saturated with water but aerial parts of the plants are also submerged in water
-both cause hypoxia (lack of oxygen) or anoxia (no oxygen) in plants affecting metabolic processes such as respiration and photosynthesis (require oxygen and light)
what is a compound stress
example is waterlogging or submergence, cause the obvious lack or oxygen but also cause other stresses such as nutrients less available, toxic elements (iron0 become soluble, light decrease (submergence only), turbidity (soil particles suspended - submergence only)
how do plants sense hypoxia
through oxygen sensing enzymes such as plant cysteine oxidases (PCOs), and ERF transcription factors which regulate hypoxia-response genes
what occurs in the signalling pathway following hypoxia sensing
-ERF transcription factors begin on cys residue
-under normal oxygen conditions the cys is oxidized by PCOs which is a degradation signal to the ERF transcription factors meaning they dont normally accumulate in cells
-under hypoxia there is not enough oxygen to oxidize the first cys so ERF factors accumulate in the nucleus and cause a hypoxia response
what are some plant adaptation in response to waterlogging/submergence
-metabolic (maintaining glycolysis avoids an energy crisis so fermentative pathways are activated to use pyruvate as a substitute for energy production)
-growth change (rapid elongation of leaf blades, petioles/shoots as an escape strategy from the water submergence)
-anatomy change (root and shoot anatomy change through formation of aerenchyma to help effectively diffuse the oxygen)
