Selection on floral display in insect-pollinated Primula farinosa: effects of vegetation height and litter accumulation.
Journal - Oecologia (Germany )
Grazing reduces litter thickness and vegetation height and may thereby indirectly affect reproductive success and selection on floral characters in plants with prostrate growth. Reductions in litter thickness and vegetation height should influence both the resource status of plants with leaves positioned close to the ground and the significance of inflorescence height for interactions with pollinators and seed predators. We experimentally examined how simulated grazing of surrounding vegetation affected pollen limitation, fruit predation and fecundity of short-scaped and long-scaped Primula farinosa, which differ markedly in floral display and therefore in expected attractiveness to pollinators. Litter removal and pruning of surrounding vegetation increased fruit and seed production per plant in the year of the treatment and the probability of flowering in the following year. Pollen limitation of fruit and seed production was stronger in the short-scaped morph than in the long-scaped morph, but was not significantly affected by litter removal and simulated grazing of surrounding vegetation. Supplemental hand-pollination reduced seed size in the year of the treatment and flowering probability in the second year, and these effects did not differ among scape morphs or grazing treatments. The results suggest that grazing indirectly favours seed production in P. farinosa, mainly because it increases the resource status of plants that escape damage. Contrary to expectation, there was no strong evidence that litter accumulation and tall vegetation increase the severity of pollen limitation or reduce the relative performance of the short-scaped morph.
|ISSN : ||0029-8549|
|Mesh Heading : ||Animals Feeding Behavior Flowers Fruit Insects Pollen Primula Reproduction Seeds growth & development growth & development anatomy & histology growth & development growth & development|
|Mesh Heading Relevant : ||anatomy & histology physiology physiology physiology|
Improper excess light energy dissipation in Arabidopsis results in a metabolic reprogramming
Journal - BMC Plant Biology
BackgroundPlant performance is affected by the level of expression of PsbS, a key photoprotective protein involved in the process of feedback de-excitation (FDE), or the qE component of non-photochemical quenching, NPQ.ResultsIn studies presented here, under constant laboratory conditions the metabolite profiles of leaves of wild-type Arabidopsis thaliana and plants lacking or overexpressing PsbS were very similar, but under natural conditions their differences in levels of PsbS expression were associated with major changes in metabolite profiles. Some carbohydrates and amino acids differed ten-fold in abundance between PsbS-lacking mutants and over-expressers, with wild-type plants having intermediate amounts, showing that a metabolic shift had occurred. The transcriptomes of the genotypes also varied under field conditions, and the genes induced in plants lacking PsbS were similar to those reportedly induced in plants exposed to ozone stress or treated with methyl jasmonate (MeJA). Genes involved in the biosynthesis of JA were up-regulated, and enzymes involved in this pathway accumulated. JA levels in the undamaged leaves of field-grown plants did not differ between wild-type and PsbS-lacking mutants, but they were higher in the mutants when they were exposed to herbivory.ConclusionThese findings suggest that lack of FDE results in increased photooxidative stress in the chloroplasts of Arabidopsis plants grown in the field, which elicits a response at the transcriptome level, causing a redirection of metabolism from growth towards defence that resembles a MeJA/JA response.
Relationships between population size and pollen fates in a moth-pollinated orchid
Journal - Biology Letters
Management of small plant populations requires an understandingof their reproductive ecology, particularly in terms of sensitivityto Allee effects. To address this issue, we explored how componentsof pollen transfer and pollination success of individual plantsvaried among 36 populations of the self-compatible moth-pollinatedorchid Satyrium longicauda in South Africa. Mean fruit set,seed production, proportion of flowers with pollen depositedor removed and proportion of removed pollen that reached stigmas(approx. 8% in this species) were not significantly relatedto population size (range: 1–450 flowering individuals),density or isolation. Plants in small populations did, however,have significantly higher levels of pollinator-mediated self-pollination(determined using colour-labelled pollen) than those in largerpopulations. Our results suggest that small populations of thisorchid species are resilient to Allee effects in terms of overallpollination success, although the higher levels of pollinator-mediatedself-pollination in small populations may lead to inbreedingdepression and long-term erosion of genetic diversity.
|Keywords : ||Allee effects • pollen transfer efficiency • pollination • population ecology • Satyrium • self-pollination|
The effects of nectar addition on pollen removal and geitonogamy in the non-rewarding orchid Anacamptis morio
Journal - Proceedings of the Royal Society B: Biological Sciences
It has been suggested that the absence of floral rewards inmany orchid species causes pollinators to probe fewer flowerson a plant, and thus reduces geitonogamy, i.e. self–pollinationbetween flowers, which may result in inbreeding depression andreduced pollen export. We examined the effects of nectar additionon pollinator visitation and pollen transfer by tracking thefate of colour–labelled pollen in Anacamptis morio, anon–rewarding orchid species pollinated primarily by queenbumble–bees. Addition of nectar to spurs of A. morio significantlyincreased the number of flowers probed by bumble–bees,the time spent on an inflorescence, pollinarium removal andthe proportion of removed pollen involved in self–pollinationthrough geitonogamy, but did not affect pollen carryover (thefraction of a pollinarium carried over from one flower to thenext). Only visits that exceeded 18 s resulted in geitonogamy,as this is the time taken for removed pollinaria to bend intoa position to strike the stigma. A mutation for nectar productionin A. morio would result in an initial 3.8–fold increasein pollinarium removal per visit, but also increase geitonogamousself–pollination from less than 10% of pollen depositionsto ca. 40%. Greater efficiency of pollen export will favourdeceptive plants when pollinators are relatively common andmost pollinaria are removed from flowers or when inbreedingdepression is severe. These findings provide empirical supportboth for Darwin's contention that pollinarium bending is ananti–selfing mechanism in orchids and for the idea thatfloral deception serves to maximize the efficiency of pollenexport.
|Keywords : ||deception • Orchidaceae • pollen carryover • pollination • pollinia • pollinator behaviour|