Vernalisation Experiment
Background
Being able to describe the development of crops is an important skill for agronomists. Recommendations for timing of fertiliser application or herbicide application often depend on the stage of development of the crop. Timing of fertilizer application (eg. nitrogen) will be determined by the growth stage of the crop and its effect on source-sink relation. Also, being able to estimate time of flowering of a crop would help to select crops/varieties on their maturity to minimize the risk of frost stress on the crop at flowering time. Some crop cultivars, however, require the accumulation of cold temperature (ie. vernalisation) in order to flower and these cultivars are commonly called winter varieties.
Rationale
The aim of this practical is to develop an understanding of the influence of an environmental signal such as vernalisation on flower initiation and flowering (a switch from vegetative to a reproductive stage). Also, the application of skills in describing the phenology of wheat and canola will be undertaken in this exercise.
Summary of Task
In this prac you will monitor the development of 2 cultivars of wheat and 2 cultivars of canola which have been grown for different lengths of times for up to 6 weeks in cold temperatures. You will learn how to use the Zadok and BBCH decimal code scales for describing wheat and canola development (ie. phenology), respectively. The observations and measurements that you will made during this practical will be summarised as a written report.
Task
Six seeds of two wheat cultivars (EGA Wedgetail and Scepter) and of two canola cultivars (Archer and Hyola970) were sown into each of 2, 10” pots and placed in plant growth cabinet at a day/night temperatures of 4/10 °C for different time intervals. After each sowing, the 2 pots were placed in the growth cabinet at 2, 4, 8, 12, 16, 21, 28, 35 and 42 days. Also, 2 pots of each cultivar were sown and at the first sowing time and kept in growth cabinet at 20°C
Plant Growth Chamber (Cold temp):
- Day/night temperatures of 4/10°C
- Photoperiod: 16 hrs
- PAR at canopy level: 400
- Time intervals (days) 0, 2, 4, 8, 12, 16, 21, 28, 35 and 42 days
Plant Growth Chamber (Normal):
- Day/night temperatures of 15/20°C
- Photoperiod: 16 hrs
- PAR at canopy level: 400
- To be sown in conjunction with the 42 days treatment
The first sowing (42 days treatment) was done on 24 January.
Upon completion of the temperature treatment all pots were transferred from the growth chamber to the glasshouse (time period of low temperature exposure). At that time, another set of pots was sown and place in the glasshouse. This constituted the ‘0’ day temperature treatment.
Thus, the experiment is composed of 2 species, 2 varieties, 1 low temperature treatment and 8 temperature exposures and 2 reps. In each day when the experiment is to be monitored, you will need to record the average growth stage by using the decimal code scale for each pot. We will cover the use of the scale at prac time.
One of the key observations and/or measurements to be reported includes the numbers of days to when the first anther is visible (for wheat) or when the first flower opens (for canola), ie. anthesis.
You are required to submit a report of this practical (see Subject Outline for due date). Make sure that it contains the following sections: a brief Introduction, Results (with figures/tables) and a Discussion with appropriate scientific references. A marking rubric is available in the subject outline.
Some of the issues that you will need to address in the report include:
- What advantage(s) does vernalisation confers on a variety?
- Using the data you have collected, what effect did the length of temperature exposure had on the development of the wheat/canola cultivars?
- Were these results expected?
- Do any of the cultivars required ‘vernalisation’ to flower?
- Is the vernalisation requirement obligatory or facultative?
Further details of the experimental protocol will be provided during the practical.
NOTES
Cereals
Phenological growth stages and BBCH-identification keys of cereals: (wheat = Triticum sp. L., barley = Hordeum vulgare L., oat = Avena sativa L., rye = Secale cereale L.)
Code Description
Principal growth stage 0: Germination
00 Dry seed (caryopsis)
01 Beginning of seed imbibition
03 Seed imbibition complete
05 Radicle emerged from caryopsis
06 Radicle elongated, root hairs and/or side roots visible
07 Coleoptile emerged from caryopsis
09 Emergence: coleoptile penetrates soil surface (cracking stage)
Principal growth stage 1: Leaf development1, 2
10 First leaf through coleoptile
11 First leaf unfolded
12 2 leaves unfolded
13 3 leaves unfolded
1 . Stages continuous till . . .
19 9 or more leaves unfolded
Principal growth stage 2: Tillering3
20 No tillers
21 Beginning of tillering: first tiller detectable
22 2 tillers detectable
23 3 tillers detectable
2 . Stages continuous till . . .
29 End of tillering. Maximum no. of tillers detectable
Principal growth stage 3: Stem elongation
30 Beginning of stem elongation: pseudostem and tillers erect, first internode begins to elongate, top of inflorescence at least 1 cm above tillering node
31 First node at least 1 cm above tillering node
32 Node 2 at least 2 cm above node 1
33 Node 3 at least 2 cm above node 2
3 . Stages continuous till . . .
37 Flag leaf just visible, still rolled
39 Flag leaf stage: flag leaf fully unrolled, ligule just visible
Principal growth stage 4: Booting
41 Early boot stage: flag leaf sheath extending
43 Mid boot stage: flag leaf sheath just visibly swollen
45 Late boot stage: flag leaf sheath swollen
47 Flag leaf sheath opening
49 First awns visible (in awned forms only)
Principal growth stage 5: Inflorescence emergence, heading
51 Beginning of heading: tip of inflorescence emerged from sheath, first spikelet just visible
52 20% of inflorescence emerged
53 30% of inflorescence emerged
54 40% of inflorescence emerged
55 Middle of heading: half of inflorescence emerged
56 60% of inflorescence emerged
57 70% of inflorescence emerged
58 80% of inflorescence emerged
59 End of heading: inflorescence fully emerged
Principal growth stage 6: Flowering, anthesis
60 Beginning of flowering: first anther visible
61 Beginning of flowering: first anthers visible
65 Full flowering: 50% of anthers mature
69 End of flowering: all spikelets have completed flowering but some dehydrated anthers may remain
Principal growth stage 7: Development of fruit
71 Watery ripe: first grains have reached half their final size
73 Early milk
75 Medium milk: grain content milky, grains reached final size, still green
77 Late milk
Principal growth stage 8: Ripening
83 Early dough
85 Soft dough: grain content soft but dry. Fingernail impression not held
87 Hard dough: grain content solid. Fingernail impression held
89 Fully ripe: grain hard, difficult to divide with thumbnail
Principal growth stage 9: Senescence
92 Over-ripe: grain very hard, cannot be dented by thumbnail
93 Grains loosening in day-time
97 Plant dead and collapsing
99 Harvested product
1 A leaf is unfolded when its ligule is visible or the tip of the next leaf is visible.
2 Tillering or stem elongation may occur earlier than stage 13; in this case continue with stages 21.
3 If stem elongation begins before the end of tillering continue with stage 30.
LANCASHIRE, P. D., H. BLEIHOLDER, P. LANGELÜDDECKE, R. STAUSS, T.VAN DEN BOOM, E.WEBER und A.WITZENBERGER, 1991: An uniform decimal code for growth stages of crops and weeds. Ann. Appl. Biol. 119, 561–601.
WITZENBERGER, A., H. HACK und T. VAN DEN BOOM, 1989: Erläuterungen zum BBCH-Dezimal-Code für die Entwicklungsstadien des Getreides – mit Abbildungen. Gesunde Pflanzen 41, 384–388.
ZADOKS, J. C., T. T. CHANG, and C. F. KONZAK, 1974: A decimal code for the growth stages of cereals. Weed Research 14, 415–421 and Eucarpia Bulletin No. 7, 49–52.
Canola
BBCH decimal system – growth stage developed by BASF, Bayer, Ciba-Geigy and Hoechst
(From Canola Council of Canada, www.canola-council.org)
- Germination: sprouting development
00 Dry seed (seed dressing takes place at this stage)
01 Seed imbibition (water absorption)
03 Seed imbibition complete
05 Radicle (root) emerges from seed
06 Elongation of root, formation of root hairs and/or lateral roots
07 Hypocotyl with cotyledons break though seed coat
08 Hypocotyl with cotyledons grow toward soil surface
09 Cotyledons break through soil surface
Growth Stage 1: Leaf Development
10 Cotyledons completely unfold
11 First true leaf unfold
12 Two leaves unfold
13 Three leaves unfold
14 Four leaves unfold
15 Five leaves unfold
16 Six leaves unfold
17 Seven leaves unfold
18 Eight leaves unfold
19 Nine or more leaves unfold
Growth Stage 2:
This growth stage (20-29) refers to the development of side shoots and occurs in many plant species (tillering), but it is not applicable to the spring canola varieties grown in Australia.
Growth Stage 3: Stem Elongation
33 Stem elongation (bolting) begins
34 Stem 10% of final length
35 Stem 20% of final length
36 Stem 30% of final length
37 Stem 40% of final length
38 Stem 50% of final length
39 Stem 60% of final length
40 Stem 70% of final length
41 Stem 80% of final length
42 Maximum stem length
Growth Stage 4:
This growth stage (40-49) is not important for canola management but has meaning for the development of harvestable vegetative plant parts such as broccoli or cauliflower.
Growth Stage 5: Inflorescence Emergence
50 Flower buds present, but still enclosed by leaves
51 Flower buds visible from above (green bud)
52 Flower buds free, level with the youngest leaves
53 Flower buds raised above the youngest leaves
55 Individual flower buds (main inflorescence) visible but still closed
58 Individual flower buds (secondary inflorescence) visible but closed
59 First petals visible, but flower buds still closed (yellow bud)
Growth Stage 6: Flowering
60 First flower opens
61 10% of flowers on the main raceme open, main raceme elongating
63 30% of flowers open on the main raceme
65 Full flowering – 50% of flowers on main raceme open, older petals falling
67 Flowering declining – majority of petals fallen
69 Flowering ends
Growth Stage 7: Development of seed
70 0% of pods reach final size
71 10% of pods reach final size
72 20% of pods reach final size
75 50% of pods reach final size
77 77% of pods reach final size
79 Nearly all of the pods reach final size
Growth Stage 8: Ripening
80 Ripening begins – seed green, filling pod cavity
81 10% of pods ripe, seeds black and hard
83 30% of pods ripe, seeds black and hard
85 50% of pods ripe, seeds black and hard
87 70% of pods ripe, seeds black and hard
89 Fully ripe – nearly all pods ripe, seeds black and hard
Fig. 1 (Previous pages). Growth stage of canola. From Compendium of Growth Stage Identification Keys for Mono- and Dicotyledonous Plants – Extended BBCH scale, 2nd Edition1997, electronic version elaborated by M. Enz and Ch. Dachler, Novartis.
