Primula Palinuri Research Articles

Seed germination and seedling roots traits of four species living on Mediterranean coastal cliffs

We examined seed germination and seedling root morphology of Crithmum maritimum, Dianthus rupicola, Primula palinuri and Eokochia saxicola. Specifically, we tested seed germination at five different solutions (distilled water; 20/80 v/v sea water/distilled water; 30/70 v/v; 50/50 v/v; sea water). Recovery of not germinated seeds when incubated in distilled water was assessed too. We also examined the seed germination at harvesting time, and four and 12 months later. Finally, we analysed the seedling root morphology at 8 and 12 days from seed imbibition. Salinity strongly inhibited germination in P. palinuri, while had minor effects on E. saxicola, C. maritimum and D. rupicola. Apart from E. saxicola, seeds remained viable for longer than a single reproductive cycle of the species. Only C. maritimum and D. rupicola have seedling roots capable of ensuring a strong adhesion to rock from the beginning of their development; seedling roots of P. palinuri and E. saxicola seem to do not have specific traits for anchoring the seedlings in the germination site. Our data revealed some weakness in P. palinuri and E. saxicola, two species threatened with extinction and included in European and international policy instruments. We found no such criticalities in the two other species.

Serotiny in Primula palinuri: How to Face the Dry Season on Mediterranean Cliffs

Primula palinuri Petagna is the only Mediterranean and maritime species in the genus Primula, is endemic to coastal cliffs of southern Italy, and is classified as endangered with a decreasing population trend in the IUCN Red List. For this species, the major bottleneck for long-term survival has been recognized to be recruitment failure. In this study, we investigated the seed release strategy of P. palinuri, by using field observations and laboratory experiments. We hypothesized that repetitive cycles of wet/dry conditions and external wax removal could be the environmental triggers of capsule dehiscence. Data showed that capsules treated with wet/dry cycles dehisced within 75 days, while none subjected to constant dry conditions dehisced. Once dehisced, capsules repetitively closed when made wet, and opened again upon drying. Seeds of P. palinuri can remain on plant up to 2 years, over which time capsules reclose when rained upon and reopen upon drying, highlighting the first reported occurrence of serotiny in a Primula species. Serotiny allows P. palinuri to face the dry season, by avoiding capsule dehiscence during the summer dry period and delaying seed release until the beginning of fall, when water availability in the soil is generally no longer a limiting factor.

Fiber-optic refractometer for in vivo sugar concentration measurements of low-nectar-producing flowers.

Sugar concentration in floral nectars is an assessment required in several diverse fields of application. The widely used analysis, consisting of nectar extraction with a microcapillary and sugar concentration measurement with a light refractometer, is not reliable when the nectar is secreted in small quantities, unextractable with a microcapillary. Ancillary methods adopted in such cases are destructive, rather complicated and often provide much less precise and accurate results. The microscopic-size, low cost and biocompatibility of optical fibers were exploited to deliver light directly inside the flower with minimal invasiveness and measure instantaneously the refractometric properties of the nectar without extracting it. After comparing the new and old methods using two known nectariferous species, the new approach was validated on Primula palinuri, whose nectar is unextractable with microcapillaries. The fiber-optic probe was able to measure the nectar refractive index in P.palinuri flowers making it possible to highlight a previously undetected significant trend of the sugar concentration throughout the long anthesis of the single flowers. Changes in nectar concentrations are similar in both longistylous and brevistylous flowers. The fiber-optic refractometer is an advancement of light refractometer analysis. Further customization of the laboratory set-up into portable equipment will boost applications.

Full light and soil drought constrain plant growth in Mediterranean cliffs: the case of Primula palinuri Petagna

In any biogeographical region, cliffs shelter a larger number of relict species than do the surrounding areas. To develop effective conservation strategies, experimental studies are needed. We focused on Mediterranean coastal cliffs and on Primula palinuri Petagna, an endangered narrow-endemic plant, included in the IUCN Red List and chosen as a key species. The hypothesis was that light intensity and soil water availability could affect survival and growth of juvenile plants. To avoid the bias of other cliff environmental factors and to overcome problems of cliff site inaccessibility, we performed an ex-situ experiment. The effect of two light regimes and two soil water availability conditions on survival and morpho-functional traits were analysed. Plants grown under reduced light intensity and wet soil showed no reduction in survival and performed very well in terms of growth and storage accumulation. By contrast, full light and dry soil proved to be detrimental conditions. Overall results suggested that cliff environmental conditions play an important role in conservation of narrow-endemic species. The decreasing trend of the already severely fragmented populations of P. palinuri and the ongoing increasing aridity is likely to contribute to a further reduction of the already narrow distribution this cliff relict species.

Reproducing under a warming climate: long winter flowering and extended flower longevity in the only Mediterranean and maritime Primula.

Under the pressure of global warming, general expectations of species migration and evolution of adaptive traits should always be confirmed with species-specific studies. Within this framework, some species can be used as study systems to predict possible consequences of global warming also on other relatives. Unlike its mountain congeneric, Primula palinuri Petagn. has endured all the climatic fluctuations since the Pleistocene, while surviving on Mediterranean coastal cliffs. The aim of this work was to investigate the possible evolution of reproductive biological and ecological traits in P.palinuri adaptation to a warmer environment. Data showed that flowering starts in mid-winter; single flowers remain open for over a month, changing from pendulous to erect. The number of insects visiting flowers of P.palinuri increases during the flowering season, and pollination reduces flower longevity. Overall, the best pollen performances, in terms of viability and germinability, occur at winter temperatures, while pollinator activity prolongs flowering until spring. Moreover, extended longevity of single flowers optimises reproductive success. Both phenotypic plasticity and selective processes might have occurred in P.palinuri. However, we found that reproductive traits of the only Mediterranean Primula remain more associated with cold mountain habitats than warm coastal cliffs. Given the rapid trend of climate warming, migration and new adaptive processes in P.palinuri are unlikely. Response to past climate warming of P.palinuri provides useful indications for future scenarios in other Primula species.

Assessment of distyly syndrome in Primula palinuri Petagn. a rare species living on maritime vertical cliffs

The distinctive habitat of vertical cliffs provides refuges for many relict plant species. Primula palinuri Petagn. is the only maritime and Mediterranean species of the genus Primula. It only occurs on the cliffs of a narrow area of southern Italy and is classified as being at risk of extinction. Given that only fragmentary information on the biology and ecology of P. palinuri is available, we studied flower morphology, breeding system and other reproductive traits of this species to furnish data for the evaluation of its conservation status. We assessed that plants of P. palinuri develop either long-styled or short-styled flowers and both morphs are equally represented in the studied populations. Reciprocal position of anthers and stigmas is complemented by differences in pollen–ovule ratios, pollen size and exine ornamentation. In both morphs, about 90 % of open-pollinated flowers developed mature capsules and the average number of seeds per capsule was around sixty. Hand pollination experiments showed that reproductive success was high (92.86 and 100 % fruit set) following inter-morph crossings, but no fruit develops after same-morph pollination or selfing. We have ascertained that full distyly syndrome (distinct floral morphs, intra-morph incompatibility and morphs equally represented in the populations) occurs in P. palinuri. However, a further reduction of the severely fragmented range, any rapid change of the environmental conditions due to human impact on coastal areas or stochastic events of plant mortality may alter the proportion of the two morphs, affecting the fragile conservation status of the species.

Occurrence of Morphological and Anatomical Adaptive Traits in Young and Adult Plants of the Rare Mediterranean Cliff SpeciesPrimula palinuriPetagna

Cliffs worldwide are known to be reservoirs of relict biodiversity. Despite the presence of harsh abiotic conditions, large endemic floras live in such environments. Primula palinuri Petagna is a rare endemic plant species, surviving on cliff sites along a few kilometres of the Tyrrhenian coast in southern Italy. This species is declared at risk of extinction due to human impact on the coastal areas in question. Population surveys have shown that most of the plants are old individuals, while seedlings and plants at early stages of development are rare. We followed the growth of P. palinuri plants from seed germination to the adult phase and analysed the morphoanatomical traits of plants at all stages of development. Our results showed that the pressure of cliff environmental factors has been selected for seasonal habitus and structural adaptive traits in this species. The main morphoanatomical modifications are suberized cell layers and accumulation of phenolic compounds in cell structures. These features are strictly related to regulation of water uptake and storage as well as defence from predation. However, we found them well established only in adult plants and not in juvenile individuals. These findings contribute to explain the rare recruitment of the present relict populations, identifying some of the biological traits which result in species vulnerability.

Insect visitors to the rare plant Primula palinuri Petagna (Primulaceae) in southern Italy: a framework for future research

(2012). Insect visitors to the rare plant Primula palinuri Petagna (Primulaceae) in southern Italy: a framework for future research. Journal of Apicultural Research: Vol. 51, No. 3, pp. 280-281.

Two Novel Natural Flavonoids from Primula palinuri

The farinose exudate produced by Primula palinuri was found to consist of 12 flavones at least. Two of them are novel natural compounds, 2′-hydroxy-2-methoxychalcone and 8,2′,5′-trihydroxyflavone 5′-benzoate. The structure was determined by analysis of MS and 2D NMR spectral data and spectral comparison with the known compounds.

Carbon dioxide gas exchange and the energy status of leaves of Primula palinuri under water stress

The photosynthetic rate of water stressed leaves of Primula palinuri was reduced drastically by stomatal closure, not by limitations imposed on the capacity of the photosynthetic apparatus, when water loss exceeded 20% of the water content of turgid leaves. The sudden decrease in phtosynthesis was not observed when the lower epidermis of the leaves had been removed. In these 'stripped' leaves, inhibition of photosynthesis increased only gradually during the wilting caused by increasing water stress and was complete when the relative water content was as low as 20% compared with the initial value. This corresponded to a water potential of about-40 bar. The light intensity at which half-maximum rates of photosynthesis were observed decreased as stress increased. In intact leaves photosynthesizing in the presence of CO2, light scattering, which is a measure of thylakoid energization, increased steeply during stomatal closure. The observed increase corresponded to the light scattering level measured in the absence of CO2. When the lower epidermis was removed, no sudden increase in thylakoid energization could be observed during dehydration. Thylakoid energization remained high even at low water potentials. It decreased drastically only below a relative water content of 20%. Irrespective, of the extent of water stress, CO2 fixation of stripped leaves increased when the oxygen content of air was reduced from 21% to 2%. Usually the transition from 21 to 2% O2 was accompanied by increased thylakoid energization. The increase in energization was more pronounced below than above a relative water content of 50%. The data show that energy-dissipating photorespiratory CO2 turnover in the in tercellular space of water-stressed leaves whose stomata are closed decreases only slowly as water stress increases. Respiratory CO2 production by leaves in the dark was even more resistant to water stress than photosynthesis. It was still significant at water potentials as low as-80 bar.

Hexaploid populations of « Primula palinuri » Petagna in some recently discovered stations from its Thyrrenian range

Summary Plants of Primula palinuri Petagna, collected from some recently discovered stations of the Italian Thyrrenian coast, were found to be exclusively hexaploid (2n = 66). The taxonomic position of this species and its relationships with the other entities of the genus Primula are discussed.

Der Diffusionswiderstand der Spalt�ffnungen; ein Vergleich des CO2-Gaswechsels von Bl�ttern mit und ohne Epidermis

The lower epidermis from leaves of Primula palinuri can be stripped off. Light-saturation curves of the CO2-exchange were measured at 20°C and 300 ppm CO2. Whereas the normal leaf reaches light-saturation at 0.3 cal cm-2 min-1, even 0.6 cal cm-2 min-1 is not sufficient to saturate the stripped leaf. Transpiration, apparent CO2-uptake and leaf-temperature were measured simultaneously. The data were used to calculate the diffusion resistances for CO2 with the usual methods, that is, from the diffusion resistances for water-vapour transport. The comparison of the CO2-exchange of stripped and normal leaves makes it possible to determine the resistances—in particular those of the stomata—directly from the CO2-exchange. Both methods agree well. When CO2 exchanges only through the lower surface of the leaf the epidermis is—even with opened stomata—a considerable diffusion resistance. It lowers the CO2-concentration in the intercellular system to 160 ppm and limits the CO2-uptake.