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SEED DORMANCY IN COMMERCIAL VEGETABLE AND FLOWER SPECIES - Coggle Diagram
SEED DORMANCY IN COMMERCIAL VEGETABLE AND FLOWER SPECIES
PRIMARY
combinational dormancy (two or more types of primary dormancy)
break dormancy
all blocking conditions must be eliminated in proper sequence
warm (more than 15°C) or cold (1-10°C) conditions
Morphophysiological
simple
epicotyl
epicotyl and radicle
exo-endodormancy
endogenous (factors inside embryo)
physiological
After ripening - time require for seeds in dry storage to lose dormancy
break dormancy
stratification - seeds are placed between layers of moist sand or soil in boxes and exposed to chilling temperatures (outdoor/refrigeratos)
exposure of imbibed seed to red light (625 to 700nm)
photodormant - requires light or dark condition for germination
categories
intermediate
non-deep (most common)
deep
physiological changes within embryo that results in change in its growth potential - allows radicle to escape restraint of seed coverings
morphological
aids to induce germination
treatment with chemical additives (potassium nitrate/gibberelic acid)
exposure to temperatures of less than 15°C
rudimentary or undeveloped embryos
embryo has not completed development at the time seed is shed from plant
exogenous (factors outside embryo)
treatments to overcome dormancy
concentrated sulfuric acid
alternate freezing or thawing
mechanical abrasion
endosperm, perisperm. outer integuments of seed coat or fruit pericarp may become hard or fibrous
tissues outside embryo inhibit water uptake, mechanical restraint, modify gas exchange and prevent leaching of inhibitors from embryo
SECONDARY
prevent germination of seeds when environmental conditions are not favourable for seedling growth
environmental conditions
unfavourable temperature
prolonged light or darkness
water stress
anoxia
break dormancy
chilling
light
treatment with gibberellic acid
thermodormancy
will not germinate when temperature returns to near optimum temperatures
light-induced dormancy
for some seeds, if exposed to light for a period of time, they enter secondary dormancy
Conditional dormancy
change in ability to germinate related to time of the year