Crop Growth and Flowering Flashcards
What are growing degree days (GDD)
GDD: a measure of accumulated thermal units during the growing season that is correlated with plant development
GDD calculation
Heat units= (max. temp + min. temp) / 2- base
*Min temp less than 50 are set at 50. Max temp higher than 86 are set at 86.
Why is it important to know crop growth statges? How are GDD related to growth stages?
To describe crop development.
To use as a guide to when to apply management treatments.
(ex. when to apply fertilizers or herbicides, when to irrigate)
photoperiodism
actual response in nyctoperiodism.
Plants will flower not according to a certain length of photoperiod but based on whether or not the photoperiod is longer or shorter than a certain length required by the species
Short Day Plants
flowering stimulated by day lengths shorter than a critical max.
Can be modified by temp. ex. soybeans, corn, sorghum
Long Day Plants (LDP)
flowering stimulated by day lengths longer than a critical max.
ex. winter annuals (wheat, barley, etc. ) biennials
Short-Long day Plants
flowering in response to a period of short days followed by long days.
Ex. many temperate perennial grasses; orchard grass; tall fescue
Long- short day plants
flowering in response to a sequence of long days followed by short days
ex. night jasmine
day neutral plants
flowering is insensitive to photoperiod
ex. dandelion, tomato
P far red (Pfr)
Absorbs light at 720-750 nm
Inhibits flowering in SNP
Promotes flowering in LDP
Inhibits growth of mesocotyl in some cereal species
Pred (Pr)
Absorbs light at 600-680nm
Promotes flowering in SDP
Inhibits flowering in LDP
More stable and biologically active form
Floral induction
production of a flowering stimulus (Chemical change) by cold or day length
Flower initiation
Transformation of vegetative growing points (meristems) into floral primordia in response to temp and photoperiod
Vernalization
The requirement of a cold treatment to stimulate flowering
Generally 2-6 weeks below a critical temp (approx. 45 degrees F)
Indeterminate
vegetative growth on main stem continues after flowering has initiated
- traditionally represented by northern maturity groups of soybean