13 Flashcards
If you have higher ABA/GA ratio, does germination occur?
No
If you have lower ABA/GA ratio, does germination occur?
Yes
Gibberellin is important for germination, but it is also important for? 2*
*Cell elongation
*Flowering
What really is a seed?
Its an embryonic plant that is now a diploid tissue by fusing of male and female gametes which were haploid.
Seed anatomy? 4*
*Seed coat: what is interacting with the environment and is important in first defense of seed against that environment.
*Embryo: What will start producing roots and shoots. The only alive tissue of the seed where gibberellins will be produced.
*Endosperm: food storage of the plant.
*Aleurone: Source of the a-amylase enzyme used to break down starch into sugars.
seed germination requires? 4*
*rehydration, *oxygen, *suit temperatures, and *demobilization of energy reserves.
What conformation of the red light absorbing chromophore facilitates germination?
Pfr
germination is induced/inhibited by gibberellin?
Induced
Steps for plant germination?
Seed absorbs water and oxygen and germination begins. Then, gibberellin diffuse from embryo to cells in aleurone layer. The aleurone cells synthesis and release digestive enzyme a-amylase to the endosperm. a-amylase digest starch, and release sugars and other molecules to growing plant.
Is ratio or quantity more important in hormones?
Ratio
If you have a high ABA/GA ratio, then?
Seed dormancy
If you have a low ABA/GA ratio?
Seed germination
What does ABA do in the seed?
inhibits the synthesis of a-amylase in the aleurone layer. No nutrients will be available for germination.
Precocious germination vivipary14 (vp14) mutant of maize encourages germination with ABA acid being present by?
Vp14 being an ABA deficient mutant and also over-produces GA.
ABA synthesized in roots travels using the _____ and promotes stomatal closing even in presence of water?
Xylem
in the stomata, how does it open in presence of blue light?
Blue light phosphorylation pHOT1/PHOT2 and H+ pumping by H+-ATPase increase. This creates a gradient to import K+ and Cl-. K+ goes in electrochemical gradient while Cl- goes against and goes in by a cotransporter. Solute potential decrease, water potential decrease, turgor pressure increase, and guard cells increase in size.
How does stomata close when ABA is present?
ABA is sensed by an ABA receptor that inhibits H+ pumping by H+-ATPases. Inward-directed H+/Cl- cotransporters stop working and outward directed Cl- channels open. Cl- exits along its favorable electrochemical gradient. The change in membrane potential closes inward-directed K+ channels and opens outward-directed K+ channels. K+ exits in its favorable electrochemical gradient. Solute potential in guard cells increase, water potential increase, water leave guard cell. This decreases turgor pressure within the guard cell. Guard cells shrink.
Cytokinins (CKs) are regulators of leaf senescence. Senescence is?
Senescence is? A mechanism that involves degradative biochemical processes that lead to death. It is sensed by environment or natural response due to aging.
stages of leaf senescence?
*initiation phase: transition from nutrients sink to nitrogen source cells. Photosynthesis declines and early signaling events.
*Degenerative phase: dismantling of cellular constituents degradation of macromolecules.
*terminal phase: loss of cellular integrity; cell death; leaf abscission (shedding).
What light typically gets absorbed by leaves that do not have chlorophyll?
The light blues and some greens.
treatments with cytokinin in plants do what?
delay leaf senescence
ethylene gas in plants do?
promote fruit ripening.
Ripening in fruits describe what?
the transition to aging and death of plant tissues. This facilitates reproduction by facilitating seed dispersal and preparing the seed-bearing organ for detachment from the plant.
do all fruits require ethylene for ripening?
No. non ethylene ripening plants ripen by ABA.
Climacteric fruit?
ripen by a response of ethylene.
what is the structure of ethylene?
gaseous, non-polar, hydrophobic molecule that freely diffuses across the plasma membrane.
