2.2 Seed Germination

8/2/2019 2.2 Seed Germination

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Prepared by Lucy MwauraFor

Allanblackia domesticationworkshop23rd to 27th Oct 2006

Allanblackiaseed germination

protocols


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Outline AB seed physiology

Conditions required for germination.

Possible Allanblackia seed dormancy Seed germination treatments

applied by partcipating countries

Treatment methods that have beenuse on a large scale

Lesson learnt


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Allanblackia seed physiology Fruit/seed weight

Seed moisture

Storage

Dormancy

Germination


4/18

Fruit/seed weight-A single seed weightranged between 5-

10grams when fresh-A kilo of fresh seedshad between 90-100seeds

-viable seeds per kilo?(not confirmed)

-fruit weight rangedbetween 2.5-5.5kg


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Moisture content

Seed moisture

-AB seed had moisturecontent of up to 40% whenfresh.

-Loss of seed moisture wasfound to be proportional toloss in viability (desiccationtolerance trial/biochemicaltest 2004 )

-The rate of moisture loss ishigh soon after extraction,and decreased with time ofexposure to air.


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Storage trials Storage

- Extracted seeds can bestored at -20oC inairtight aluminum bagsfor at least one yearwithout loss of moistureand viability. (desiccationtolerance test of 2004) .-Seeds remained viable

with high moisture whilestill enclosed in the fruitburied, in moist soil/sandfor three months.


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Conditions required forseed germination In Tanzania and Kenya use of moist sand

media has been used to pre-germinate seeds The germination beds should remain moist

during this period, however minimum wateringis recommended to avoid water logging( seedwould rot)

Seeds in nursery beds should be put under

shade. (In Tanzania seeds are covered withdried banana leaves). Temperatures should be between 25-30

degrees Celsius.


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AB possible seeddormancy Dormancy-is the physiological state that prevents normal growth

of most seeds when all the conditions are favorable.

Seed coat dormancy: gelatinous sticky substances foundon seeds could contain chemical inhibitory compunds which make theseed coat impermeable to water and gases, this growth inhibitors must beleached out to allow germination (Forest Biology journal 2000).

Embryo dormancy: have growth-inhibitors present andlack growth promoters.

-The embryo in enclosed in endocarp that contains high oil content, thiscould have chemical inhibitory compound that prevent germination-Abscisic acid contained in the embryo makes the seed dormant untilcertain native enzymes are triggered to permit breakdown of thehormones ( intensive work required here)


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Seed germination treatments

applied and results obtained by

specific countries Results from an experiment investigating the germination potential of Allanblackia

seeds in a mixture of forest soil and sand (2:1) indicated that it took 18 months forA floribundaand 19 months for A gabonensis to reach 50% germination level.

24 months after the trial was set an overall 86% of seeds germinated.Pretreatments experiments were developed to reduce the germination period

Preliminary results from pretreated seeds of AB (immersion in 90% gibberellic acid

(GA3) for 72 hours indicate that a germination rate of 48.33 % can be obtainedafter 7 months (A. floribunda).

New experiment investigating the combined effects of GA3 concentration andduration of immersion on 4800 A. floribundaseeds subjected to 3 immersiondurations and 4 GA3 concentrations in a factorial design; (experimental unit of 100seeds) is being done in Cameroon.

1. Cameroon.


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Seed germination trial in

specific countries

Out of 13 accessions sown at the nursery theoverall germination was 0.02% as at June2005.

Another 21 accessions were sown in the greenhouse with three treatments, (with testa,without testa and soaking in water for 24 hrs) inearly 2005, overall germination was 0.05% byFebruary 2006.

ITSC also put 600,000 seeds on nursery bedsof (A parviflora), only 0.1% of seedlings wastransplanted into poly tubes.

2. Ghana


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Extracted seeds are sown on seed-beds Burying the whole fruit in a hole and cover with

forest debris and then transfer germinated

seeds to the polyethylene tubes. Collecting newly emerged seeds and raise in

the polyethylene tubes( rat caches) Extracted seeds are soaked in water while

floater are discarded, the sinkers are removedand nicked on the distal end and later soakedin GA31000ppm( refer to note for GA3preparation)

Treatments that have been used on a large

scale ( best germination results so far)3 Tanzania


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Seed germination treatmentsfrom specific countries cont Germination capacity

-Seed germination capacity was low

and slow-tap root emerged first within 3-5months

-a fully developed seedling with twoalternate leaves occurred after 7

months of sowing.-seeds that did not germinate after 5months had an enlarged embryoand remained dormant

-seed stained brilliant red indicatingviable tissues with TTZ test.

4. Kenya


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Pre-sowing methods sowing without treatment

- No seed treatment has been

found effective to improvegermination percentages.-First trial 2004 done withouttreatment (germination was4%)

Sowing with treatment-seeds were stored for amonth, soaked in water 24hrs,and dried for 2 days thencracked to open the seed

coat( germination was 1%)


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Pre-sowing methods cont Preparation and soaking in GA-3

and KNO3

-Gibberellic acid (GA-3) wasdissolved in 1 ml ethyl-alcohol/water

250ppm, 500ppm,1000ppm( refer tonotes)

-Potassium nitrate(KNO3 )

0.2%,0.5%,and 1%(ref: ISTA newsbulletin No 130 Oct 2005)

-Combined treatment (KNO30.2% and250ppm)

-one seedlot was not treated


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Treatments cont Experimental set up

-seeds were put invarious treatment andsoaked for 48hrs at roomtemperature.-Deep flower pots werefilled with sterile sand at level, sown seedswere covered with a thin

layer of sand.-similar set-up was put atthe nursery same time.


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Germination progress. Sowing

-Dec 2005, seeds were sown2 cm apart in containers, andincubated at 25C night and

30C day temperature, thesand was kept moist withoutlogging.

Monitoring

-Minimum watering with

distilled water was done.-Daily monitoring andrecording was continuouslydone.


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Germination chart

0

5

10

15

20

25

30

%germinated seeds

250ppm GA3

soak 48hrs

500ppm GA3

soak 48hrs

1000ppm GA3

soak 48hrs

KNO3 0.2%

48hrs

KNO3 0.5%

48hrs

KNO3 1.0 %

48hrs

Cold w ater

soak 48hrs

250ppm GA3

+KNO3 0.2%

48hrs

Control

Treatments

A stuhlmannii germination report


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Lesson learnt We still have a big challenge ahead of us to find ways to improve

seed germination.

Use of local knowledge practice in Tanzania is so far the bestpractice that improves seed germination.

More research needs to be done using KNO3 and GA-3treatments.

Bioassay study will be important to find out whether hormonesratios found in seeds have any influence on physiological seedactivities (germination? dormancy?).

We need to set-up seed propagators in central nurseries whereenvironmental conditions can be controlled and temperaturesmonitored.

Documents

2.2 Seed Germination