BIOL 341 Lecture 21: Flowering
21 Mar 2017
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Phases: juvenile- not capable of reproduction, adult vegetative- capable of reproduction but does not engage, adult reproductive. Causes of transitions between phases: size, nutrients, carb status, light/ photoperiod, water, temperature, hormones, mirnas, genes. Floral evocation: process that commits the sam to form flowers. Detection of day length, making it possible for an event to occur at a particular time of year: phytochrome, cryptochrome. Short-day plants (sdps): > critical night length: will flower when the length of the night is over a threshold. Avoiding ambiguities between spring and fall days: short-long-day plants (sdlps): early spring, short day followed by progressively longer days, long-short-day plants (lsdps): late summer/fall. Juvenile phase- does not mature until the proper time (e. g. until the spring: vernalization- prolonged exposure to a cold temperature. Photoperiodic time-keeping depends on a (cid:862)circadian oscillator: critical night length with an appropriately- timed dawn signal, must be continuous darkness, sdp: critical darkness is 12h (< 12h = will flower)
