The Papaveraceae comprise about 200 species of herbaceous plants and, rarely, shrubs within about 25 genera. They include species which provide an edible oil (Papaver somniferum L. subsp. hortense) and a narcotic (Papaver somniferum L. subsp. somniferum, opium poppy). The fruits are dehiscent capsules and seed storage behaviour is orthodox.
SEED DORMANCY AND GERMINATION
The seeds are small with a minute embryo surrounded by oily endosperm. Seed dormancy can be considerable, with delayed germination a common problem. B.R. Atwater classifies seed morphology as endospermic seeds with a basal rudimentary embryo (see Table 17.1, Chapter 17). Potassium nitrate, gibberellin and pre-chill treatments generally promote seed germination.
No detailed information on any one genus is provided in this chapter, but Table 54.1 provides a brief summary of recommended germination test procedures and dormancy-breaking treatments. In addition the algorithm below may be helpful in developing suitable germination test procedures for difficult accessions of the species listed in Table 54.1 and for other species.
RBG Kew Wakehurst Place algorithm
The first step in the algorithm is to test seeds at constant temperatures of 11°C, 21°C and 31°C with light applied for 12h/d. If full germination is not achieved in any one regime and the results suggest a trend in the response of germination to constant temperatures then test at a more extreme or an intermediate constant temperature as appropriate. For example, if germination at 11°C is greater than germination at 21°C or 31°C then test a further sample of seeds at a constant temperature of 6°C with light applied for 12h/d. A further example: if germination at 21°C and 31°C is roughly similar but greater than at 11°C then test a further sample of seeds at a constant temperature of 26°C with light applied for 12h/d.
If these constant temperature regimes do not promote full germination then the second step of the algorithm is to test seeds in alternating temperature regimes. If germination at constant temperatures of 21°C and below was greater than at constant temperatures above 21°C in step one then test a further sample of seeds in an alternating temperature regime of 23°/9°C (12h/12h) with light applied for 12h/d. If germination at constant temperatures of 31°C was greater than at all other constant temperatures in step one then test a further sample of seeds in an alternating temperature regime of 33°/19°C (12h/12h) with light applied for 12h/d. If germination at constant temperatures of 21° to 31°C was similar or if germination at a constant temperature of 26°C was greater than at all other constant temperatures in step one then test further samples of seeds in both the alternating temperature regimes described above.
If the second step of the algorithm does not result in full germination then the third step is to co-apply 7 x 10-4 M GA3 to the germination test substrate and test a further sample of seeds in the most successful temperature regime determined from a comparison of the results of steps one and two.
If the third step of the algorithm does not result in full germination then the fourth step is to pre-chill a further sample of seeds at 2° to 6°C for 8w and then test in the most successful regime determined from a comparison of the results of steps one to three. This may include co-application of GA3 if the results of step three show a significant increase in germination over the corresponding test in step one or two.
If full germination has not been promoted, the fifth step of the algorithm is to estimate viability using a tetrazolium test (see Chapter 11, Volume I).
If the result of the tetrazolium test indicates that the failure to achieve full germination is due to the presence of dead seeds and that one of the above regimes promoted the germination of all, or almost all, the viable seeds, then this regime is used for all subsequent germination tests. If, however, the result of the tetrazolium test indicates that dormancy has not been broken by the regimes applied so far in the algorithm, then experiment with modifications to the above regimes. Clues to possible satisfactory dormancy-breaking treatments and promotory germination test environments can be obtained from the information summarised in Table 54.1.
TABLE 54.1 Summary of germination test recommendations for species within the Papaveraceae
|
Species and Authority |
Substrate |
Temperature |
Duration |
Additional directions |
Source |
|
Chelidonium majus L. |
TP |
20°/30°C |
28d |
pre-chill |
ISTA |
|
Dendromecon rigida Benth. |
|
|
|
hot water or alkali soak |
Atwater |
|
Eschscholzia california Cham. |
TP; BP |
10°C; 15°C |
14d |
potassium nitrate |
ISTA |
|
TP |
15°C |
10d |
potassium nitrate |
AOSA |
|
|
|
15°C |
14d |
potassium nitrate, 0.2% |
Atwater |
|
|
Hunnemannia fumariifolia Sweet |
TP |
20°/30°C |
18d |
light, ensure good moisture supply |
AOSA |
|
Papaver alpinum L. |
TP |
10°C; 15°C |
14d |
potassium nitrate |
ISTA |
|
Papaver glaucum Boiss. & Haussk.
|
TP |
10°C; 15°C |
14d |
light, potassium nitrate |
ISTA |
|
TP |
15°C |
14d |
potassium nitrate |
AOSA |
|
|
Papaver nudicaule L. |
TP |
10°C; 15°C |
14d |
light, potassium nitrate |
ISTA |
|
TP |
15°C |
14d |
potassium nitrate |
AOSA |
|
|
|
15°C |
21d |
potassium nitrate, 0.2% |
Atwater |
|
|
Papaver orientale L.
|
TP |
20°/30°C; 20°C |
14d |
pre-chill, potassium nitrate |
ISTA |
|
TP |
20°/30°C |
12d |
light, potassium nitrate |
AOSA |
|
|
Papaver rhoeas L. |
TP |
20°/30°C; 15°C; 20°C |
14d |
light, potassium nitrate, pre-chill |
ISTA |
|
TP |
15°C |
8d |
|
AOSA |
|
|
|
15°C |
14d |
|
Atwater |
|
|
Papaver somniferum L. |
TP |
20°C |
10d |
pre-chill |
ISTA |
|
Romneya coulteri Harvey |
|
20°C |
155d |
pre-soak, 0.5h, 1N KOH, plus GA, 100ppm |
Atwater |
