Abstract
Common juniper (Juniperus communis L.) populations in northwest European lowlands are currently declining in size and number. An important cause of this decline is a lack of natural regeneration. Low seed viability seems to be one of the main bottlenecks in this process. Previous research revealed a negative relation between seed viability and both temperature and nitrogen deposition. Additionally, the seeds of common juniper have a variable ripening time, which possibly influences seed viability. However, the underlying mechanisms remain unresolved. In order to elucidate this puzzle, it is important to understand in which phases of seed production the main defects are situated, together with the influence of ripening time. In this study, we compared seed viability of populations with and without successful recruitment. We examined three seed phases: (i) gamete development; (ii) fertilisation and early-embryo development; and (iii) late-embryo development. After the first two phases, we found no difference in the percentage viable seeds between populations with or without recruitment. After late-embryo development, populations without recruitment showed a significantly lower percentage of viable seeds. These results suggest that late-embryo development is a bottleneck in seed development. However, the complex interaction between seed viability and ripening time suggest that the causes should be in the second seed phase, as the accelerated development of male and female gametophytes may disturb the male-female synchrony for successful mating.
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Claims 5
Claim · model-written summary
Viable seed percentages did not differ between recruitment groups after gamete development.
- Organ / stage
- first two phasese0
- Outcome
- percentage viable seedse0
- Direction
- no differencee0
- Comparator
- populations with or without recruitmente0
Not reportedTaxon
Verbatim
e0“After the first two phases, we found no difference in the percentage viable seeds between populations with or without recruitment.”
Claim · model-written summary
Viable seed percentages did not differ between recruitment groups after fertilisation and early embryo development.
- Organ / stage
- first two phasese0
- Outcome
- percentage viable seedse0
- Direction
- no differencee0
- Comparator
- populations with or without recruitmente0
Not reportedTaxon
Verbatim
e0“After the first two phases, we found no difference in the percentage viable seeds between populations with or without recruitment.”
Claim · model-written summary
After late embryo development, nonrecruiting populations had significantly lower viable seed percentages.
- Material
- populations without recruitmente0
- Organ / stage
- late-embryo developmente0
- Outcome
- percentage of viable seedse0
- Direction
- lowere0
Not reportedTaxon
Verbatim
e0“After late-embryo development, populations without recruitment showed a significantly lower percentage of viable seeds.”
Claim · model-written summary
Late embryo development was interpreted as a seed development bottleneck.
Not reportedTaxon
Verbatim
e0“These results suggest that late-embryo development is a bottleneck in seed development.”
Claim · model-written summary
Authors suggest accelerated gametophyte development may disrupt male female synchrony.
- Organ / stage
- male and female gametophytese0
- Outcome
- male-female synchrony for successful matinge0
- Qualifier
- may disturbe0
Not reportedTaxon
Verbatim
e0“the accelerated development of male and female gametophytes may disturb the male-female synchrony for successful mating.”