Crop Growth and Flowering

Question 1

What are growing degree days (GDD)

Answer 1

GDD: a measure of accumulated thermal units during the growing season that is correlated with plant development

Question 2

GDD calculation

Answer 2

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.

Question 3

Why is it important to know crop growth statges? How are GDD related to growth stages?

Answer 3

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)

Question 4

photoperiodism

Answer 4

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

Question 5

Short Day Plants

Answer 5

flowering stimulated by day lengths shorter than a critical max.
Can be modified by temp. ex. soybeans, corn, sorghum

Question 6

Long Day Plants (LDP)

Answer 6

flowering stimulated by day lengths longer than a critical max.
ex. winter annuals (wheat, barley, etc. ) biennials

Question 7

Short-Long day Plants

Answer 7

flowering in response to a period of short days followed by long days.
Ex. many temperate perennial grasses; orchard grass; tall fescue

Question 8

Long- short day plants

Answer 8

flowering in response to a sequence of long days followed by short days
ex. night jasmine

Question 9

day neutral plants

Answer 9

flowering is insensitive to photoperiod

ex. dandelion, tomato

Question 10

P far red (Pfr)

Answer 10

Absorbs light at 720-750 nm
Inhibits flowering in SNP
Promotes flowering in LDP
Inhibits growth of mesocotyl in some cereal species

Question 11

Pred (Pr)

Answer 11

Absorbs light at 600-680nm
Promotes flowering in SDP
Inhibits flowering in LDP
More stable and biologically active form

Question 12

Floral induction

Answer 12

production of a flowering stimulus (Chemical change) by cold or day length

Question 13

Flower initiation

Answer 13

Transformation of vegetative growing points (meristems) into floral primordia in response to temp and photoperiod

Question 14

Vernalization

Answer 14

The requirement of a cold treatment to stimulate flowering

Generally 2-6 weeks below a critical temp (approx. 45 degrees F)

Question 15

Indeterminate

Answer 15

vegetative growth on main stem continues after flowering has initiated
- traditionally represented by northern maturity groups of soybean

Question 16

Determinate

Answer 16

Vegetative growth on main stem stops when reproductive growth starts
- traditionally represented by southern maturity groups of soybean