The germination ecology of four Papaver taxa was studied with the aim …

• Abstract
• Introduction
• Materials and methods
• Results
• Discussion
• Conclusions
• References
• Figures
• Tables

Biology Articles » Bioclimatology » A Comparative Study of Germination Ecology of Four Papaver Taxa » Results

Results

- A Comparative Study of Germination Ecology of Four Papaver Taxa

 

Mortality
Fresh seeds germinated to 99·0 % (range 96·7–100 %, n = 150, for seed batches) when incubated with GA₃. During experiments or in final GA₃ tests a total of 1·1 % of all seeds were scored as dead. Severe mortality occurred only for P. argemone at 30/20 and 25/15 °C at continuous temperature regimes in light, where 34·0 and 16·9 % (n = 800), respectively, were scored as dead; this was observed as dead seeds, mostly during the last year, and low germination in GA₃ when tested after 900 d. In a parallel study, viability was good (average 95 % of 320 seeds tested) for the same seed batches of P. argemone when incubated for 480 d in light at 30/20 or 25/15 °C.

Continuous temperature regimes
Soon after experiments were begun, some germination ( %) occurred in light at all temperatures tested, except 30/20 °C (Fig. 1). Temperature preferences differed between taxa (Table 3); P. argemone germinated mostly at the lower and P. rhoeas and P. dubium ssp. dubium at the higher temperatures tested (Figs 1 and 2). In the course of time, the magnitude of inter-taxon differences increased when germination for P. rhoeas and P. dubium ssp. dubium increased at the higher temperatures in light (Fig. 1).

Time of collection was a significant explanatory factor for all taxa (Table 3); seeds collected in autumn germinated to a higher extent than those collected in summer (Figs 1 and 2). The importance of the taxon x light interaction (Table 3) was a result of the relative difference between taxa in germination achieved, being more pronounced in light than in darkness, even though P. rhoeas, overall, germinated the most and P. argemone the least in both light conditions (cf. Fig. 1 and Fig. 2). The taxon x temperature x light interaction was an important explanatory factor (Table 3) because P. dubium ssp. dubium germinated less at 25/15 than at 30/20 °C in light (Fig. 1), but about the same at the two temperatures in darkness (Fig. 2).

Only one of the four seed batches of P. dubium ssp. lecoqii (Alvastra, Table 1) germinated more than 15 % when provided with light. All germination for this taxon occurred in light at higher temperatures (Fig. 1). In darkness, germination for P. dubium ssp. lecoqii was approx. 10 % for the Alvastra seed batch (Table 1) at continuous 25/15 °C after 480 d or longer, and the dishes opened after 480 d at 30/20 °C had 3 % germination. Otherwise, germination of P. dubium ssp. lecoqii in darkness was less than 1 % regardless of seed batch, temperature level and time in treatment.

Responses to different climates
Light condition, time, climate, taxon, starting point and time of collection were all important explanatory factors (Table 4). Light condition was the single most important factor (Table 4), with much more germination in light (Fig. 3) than in darkness (Fig. 4). Overall, the warmer the climate the more germination occurred, both in light (Fig. 3) and in darkness (Fig. 4). In general, the taxa differed (Table 4), with P. rhoeas germinating most, and P. argemone and P. dubium ssp. dubium least and about the same. Seed batches collected during the autumn germinated more than those collected in the summer (Fig. 3).

The most important second-order interaction was climate x light (Table 4); the difference between the warm climate and the other two was relatively larger when seeds were subjected to light than to continuous darkness. Several second-order interactions that included ‘taxon’ were of importance. The taxon x climate interaction was a significant explanatory factor (Table 4) due to P. argemone, compared with P. rhoeas and P. dubium ssp. dubium, showing a relatively small difference in level of germination among the three different climates (Figs 3 and 4). The importance of taxon x start is a result of P. rhoeas being the only taxon with substantially more germination after a summer than after an autumn start in the annual cycles. Taxon x light and taxon x collection were both a result of P. rhoeas differing more, but in the same way, to different light conditions and times of collection than the other taxa.

There were three significant third-order interactions that included ‘taxon’. Taxon x climate x light was a result of P. dubium ssp. dubium germinating more and less than P. argemone in the warm and cold climates, respectively, in light (Fig. 3), while the two taxa germinated to the same magnitude in the climates in darkness (Fig. 4). Taxon x light x start and taxon x collection x start were both a result of P. rhoeas exhibiting more pronounced responses to start and collection in light than in darkness, and taxon x collection x start also by P. argemone showing a substantial difference between summer and autumn collections in darkness but not in light (cf. Fig. 3 and Fig. 4). Fourth- and fifth-order interactions were of minor importance (Table 4).

Of the four seed batches of P. dubium ssp. lecoqii only the Alvastra seed batch (Table 1) germinated to 40–80 %, which occurred during the second and third autumns in the intermediate and warm climates (Fig. 3). In darkness, the maximum germination for P. dubium ssp. lecoqii was 2–5 % for the same seed batch in the warmest climate at the two last points in time. Otherwise, germination for this taxon was less than 10 % and 1 % in light and darkness, respectively, regardless of seed batch, climate and time in treatment.

The temperature outdoors in Sweden was between the cold and the intermediate artificial climates (cf. Fig. 3 and Fig. 5), with the last summer during the study at a mean daily temperature close to the cold artificial climate. Emergence outdoors was generally low; P. rhoeas and P. argemone emerged most, P. dubium ssp. dubium little (Fig. 5) and P. dubium ssp. lecoqii nearly not at all (2 %). Emergence outdoors occurred mainly during the first and second autumns and during the first spring (Fig. 5).

 
Germination time and temperatures
There was a general difference between P. argemone and the other three taxa regarding germination temperatures, with P. argemone not germinating at high temperatures, resulting in later germination during autumn (Figs 3 and 5). During autumn in the warm climate, P. argemone germinated at 15/5 and 20/10 °C, P. dubium ssp. lecoqii and P. rhoeas at 25/15 °C, and P. dubium ssp. dubium at 25/15 °C and also at 30/20 °C in late summer (Fig. 3). In the intermediate climate, P. argemone germinated at 15/5 °C and the other three taxa at 20/10 °C during autumn, while spring germination was limited to 5/5 and 15/5 °C for P. argemone, P. rhoeas and P. dubium ssp. dubium. By contrast, P. dubium ssp. lecoqii did not germinate during spring (Fig. 3).