Elisabetta Oddo

Short-term effects of potassium fertilization on the hydraulic conductance of Laurus nobilis L.

This study reports experimental evidence on the effect of short-term potassium fertilization on potassium uptake, tissue concentration and hydraulic conductance of pot-grown laurel plants. Potassium uptake and loading into the xylem of laurel seedlings increased within 24 h after fertilization. Potassium was not accumulated in roots and leaves, but the [K(+)] of xylem sap was 80% higher in fertilized plants (+K) than in potassium-starved plants (-K), as a likely result of recirculation between xylem and phloem. Increased xylem sap [K(+)] resulted in a 45% increase in transpiration rate, a 30% increase in plant hydraulic conductance (K(plant)) and a 120% increase in leaf-specific conductivity of the shoot (k(shoot)). We suggest that this increase was due to ion-mediated up-regulation of xylem hydraulics, possibly caused by the interaction of potassium ions with the pectic matrix of intervessel pits. The enhancement of hydraulic conductance following short-term potassium fertilization is a phenomenon that can be of advantage to plants for maintaining cell turgor, stomatal aperture and gas exchange rates under moderate drought stress. Our data provide additional support for the important role of potassium nutrition in agriculture and forestry.

Regulating Internet trade in CITES species.

International trade in species that are or may be endangered by collection from the wild is regulated under the Convention on International Trade in Endangered Species of wild fauna and flora (CITES) for 176 member States (Parties). Internet commerce is a relatively new route for such trade. In 2007, the CITES Secretariat asked Parties to collect information on internet wildlife trade and report problems and implemented regulations. The reports indicated it was difficult to even approximate the influence of e-commerce on CITES-listed species (CITES Secretariat 2009). We report a case study in which we quantified international transactions over an internet auction site of CITES-listed cacti and cross-checked them with CITES trade data. Our results were both surprising and alarming. Species protected under CITES are included in different CITES appendices according to their level of threat of extinction from international trade. Taxa listed in Appendix I are endangered and wild collection could cause their extinction, and taxa listed in Appendix II either may become endangered if wild collection is not regulated or are similar in appearance to other species listed in Appendix I or II (see http://www.cites.org for full definitions). The treaty operates through the issue and control of permits that apply to regular and internet trade. Trade in wild specimens is either prohibited (species listed in Appendix I) or regulated by permits (species listed in Appendix II), although some Parties implement stricter regulations. Export permits must also be issued for certified artificially propagated plants. International trade of plants listed in Appendix I is allowed only if they are artificially propagated. Plants listed in Appendix I that are artificially propagated for commercial purposes are included in Appendix II (Article VII, paragraph 4 of the Convention), and the exporting enterprises should be registered in accordance with Resolution of the Conference of the Parties 9.19 (Revised at CoP15). Parties must submit annual reports to the CITES Secretariat listing the number and type of permits and certificates granted, the States with which such trade occurred, and the quantities and types of specimens traded. Some Parties report actual trade, whereas others report the permits issued. Trade data from these reports are stored in the CITES Trade Database (CTD) (http://www.unep-wcmc-apps.org/citestrade/). We used this information to assess the implementation of the Convention for international trade in CITES species over the internet. We investigated e-commerce in 2010 for cacti as a case study. All members of the Cactaceae, with the exception of 3 genera (Pereskia, Pereskiopsis, and Quiabentia) are listed in either Appendix I or II. We also restricted our analyses to species listed in Appendix I because an export permit is mandatory to export and import live plants. We monitored buyer–seller interactions on an internet auction site (not identified here) and recorded sales of live plants that were successfully completed and for which we could identify the plants country of origin and its destination. We compared this information with data on export permits for live plants in the CTD. Although these report trade data, rather than individual permits, they should reflect the internet trade if export permits were applied for, as required for all such transactions involving CITES Parties (the case for all transactions we recorded). Trade within the European Union does not require CITES permits, so we excluded these transaction and sales to Parties that have submitted official reservations against being regulated by CITES for certain cacti. All relevant exporting Parties had submitted their 2010 reports by the time of our analyses. We monitored 24 sellers over 6 months, twice weekly, until 1000 cacti listed in Appendix I had been sold. There were 978 such sales of a single plant, 1 sale with 6 plants, and 1 sale with 16 plants. We checked all scientific names and controlled for nomenclature differences between the names used in auctions and the official names used on CITES permits. Subspecies were noted if considered valid by the CITES cacti checklist. It is possible that the CTD records corresponding to a particular transaction actually corresponded to a different transaction with the same details. Our figures therefore represent the maximum number of transactions for which CITES export permits could have been issued. We did not check whether species were traded under permits spanning multiple years or under invalid permits, but we expected these would have only minor effects. Our data set contained roughly a quarter of the cactus plants for which CITES permits were issued in 2010. There were large discrepancies in the number of plants for which permits were issued and the number of plants traded in online transactions (Table 1). Our results suggest that only 10% of the plants traded were even potentially legal. Major discrepancies were also apparent in the number of species and number of importing and exporting countries between the online auctions and permits issued for that year (Table 1). Table 1 Sales of cacti listed on CITES Appendix I on an internet auction site and permits issued by CITES Parties in 2010 We suspect that most transactions we recorded were of artificially propagated plants. The United States was the only Range State recorded as exporting native species (approximately 8% of the recorded transactions). Few of the cacti sold that were pictured on the website had visible characteristics that could plausibly be associated with the plant being of wild origin. We therefore expect the recorded transactions to have only minor effects, if any, on wild populations. Nonetheless, an export permit is mandatory to export and import these plants. Therefore, the potentially wide scale of the illegal global trade that our results suggest should raise concerns about the adequacy of the protection for CITES species. For example, wild populations of some cacti listed in Appendix I may number only a few dozen individuals in their natural habitat (Hernandez et al. 2010), for which collectors are willing to pay high prices (Robbins 2003). Internet auction sites should be monitored more widely to investigate trade in CITES species with the aim of more effectively regulating trade in rare plants.

Seasonal pattern of mannitol and malate accumulation in leaves of two manna ash species (Fraxinus ornus L. and F. angustifolia Vahl) growing in Sicily

ABSTRACT The content of mannitol and malate was assayed enzimatically during spring, summer and autumn, in leaves of two species of ash, Fraxinus ornus L. and Fraxinus angustifolia Vahl, traditionally cultivated in Sicily for the extraction of manna. Both species contain high levels of mannitol and show, on a dry weight basis, a 65–80% increase in the summer content of this polyol. The malate content differs in the two species: in F. ornus it shows a summer increase, but it is relatively low (65–115 µmol g-1 DW), while in F. angustifolia it is higher (275–318 µmol g-1 DW), but remains more or less constant throughout the year. The results suggest that in these species, under the local field conditions, mannitol has a more relevant role than malate in the response to summer drought.

Effects of temperature on total phenolic compounds in Cystoseira amentacea (C. Agardh) Bory (Fucales, Phaeophyceae) from southern Mediterranean Sea

The aim of this study was to test the effects of temperature on phenolic content of the brown seaweed Cystoseira amentacea. Phenolic compounds are secondary metabolites involved in different protection mechanisms as, for example, against grazers, epiphytes and UV radiation. Seasonal variations of phenolic content in C. amentacea were analysed and laboratory experiments, in which C. amentacea was exposed to an increase of temperature (25°C and 30°C), were performed. Total phenolic content (TPC) was determined colorimetrically with the Folin–Ciocalteu reagent. In C. amentacea, a seasonal pattern in TPC was observed, with a maximum value in winter-spring. C. amentacea responded significantly to the temperature treatments with a consistent decrease in TPC after 48 h.

Tamarix arborea var. arborea and Tamarix parviflora: Two species valued for their adaptability to stress conditions.

The choice of stress resistant and highly adaptable species is a fundamental step for landscaping and ornamental purposes in arid and coastal environments such as those in the Mediterranean basin. The genus Tamarix L. includes about 90 species with a high endurance of adversity. We investigated the water relations and photosynthetic response of Tamarix arborea (Sieb. ex Ehrenb.) Bge. var. arborea and T. parviflora DC. growing in an urban environment. Both species showed no evidence of drought or salt stress in summer, and appeared to follow two strategies with T. arborea var. arborea investing in high carbon gain at the beginning of the summer, and then reducing photosynthetic activity at the end of the season, and T. parviflora showing lower but constant levels of photosynthetic activity throughout the vegetative season. For landscaping and ornamental purposes, we suggest T. arborea var. arborea when a fast-growing, high-cover species is necessary, and T. parviflora when less-invasive species are required.

Routes to cell death in animal and plant kingdoms: from classic apoptosis to alternative ways to die—a review

Programmed cell death is fundamental for multicellular organisms either in animal or plant kingdom. Classic apoptosis, which represents the best studied form of cell death, is dependent on caspase protease activity in animals. These proteases are not present in plants, where caspase-like activities, including metacaspases, are involved in the execution of plant cell death. Beyond apoptosis, various non-apoptotic forms of cell death also exist, including autophagy, necroptosis, pyroptosis, and ferroptosis. These types of cell death can be activated independently of apoptosis and sometimes occur when apoptosis is inhibited. Non-apoptotic forms of cell death are best characterized in animals, whereas, in plants, the literature is less extensive, but the molecular executioners of plant cell death are becoming clearer. The aim of this review is to describe different types of cell death and the mechanisms involved in animals and plants, highlighting similarities and differences in the two kingdoms. Moreover, implications of cell death pathways in cancer are discussed.

An integrated proteomic and metabolomic study to evaluate the effect of nucleus-cytoplasm interaction in a diploid citrus cybrid between sweet orange and lemon

Key messageOur results provide a comprehensive overview how the alloplasmic condition might lead to a significant improvement in citrus plant breeding, developing varieties more adaptable to a wide range of conditions.AbstractCitrus cybrids resulting from somatic hybridization hold great potential in plant improvement. They represent effective products resulting from the transfer of organelle-encoded traits into cultivated varieties. In these cases, the plant coordinated array of physiological, biochemical, and molecular functions remains the result of integration among different signals, which derive from the compartmentalized genomes of nucleus, plastids and mitochondria. To dissect the effects of genome rearrangement into cybrids, a multidisciplinary study was conducted on a diploid cybrid (C2N), resulting from a breeding program aimed to improve interesting agronomical traits for lemon, the parental cultivars ‘Valencia’ sweet orange (V) and ‘femminello’ lemon (F), and the corresponding somatic allotetraploid hybrid (V + F). In particular, a differential proteomic analysis, based on 2D-DIGE and MS procedures, was carried out on leaf proteomes of C2N, V, F and V + F, using the C2N proteome as pivotal condition. This investigation revealed differentially represented protein patterns that can be associated with genome rearrangement and cell compartment interplay. Interestingly, most of the up-regulated proteins in the cybrid are involved in crucial biological processes such as photosynthesis, energy production and stress tolerance response. The cybrid differential proteome pattern was concomitant with a general increase of leaf gas exchange and content of volatile organic compounds, highlighting a stimulation of specific pathways that can be related to observed plant performances. Our results contribute to a better understanding how the alloplasmic condition might lead to a substantial improvement in plant breeding, opening new opportunities to develop varieties more adaptable to a wide range of conditions.

Water recycling in leaves of Lithops (Aizoaceae)

Abstract Lithops plants consist of a pair of succulent leaves inserted on a short stem; in each growing season, young leaves develop in a cavity formed between the older pair. Young leaves can take up water from the older pair allowing the plant to maintain growth and leaf expansion even without external supply of water. Recycling water between vegetative organs is one of the possible adaptation strategies of plants under drought stress, but it had never been demonstrated experimentally in Lithops. The methodology used to verify the existence of water redistribution from old leaves to young leaves was fluorescence microscopy, using two dyes to follow the water pathway inside the plant: Sulforhodamine G (SRG) and 5(6)-carboxyfluoroscein diacetate (CFDA). In Lithops fluorescent tracers loaded into old leaves were found in young leaves, in 74% of the cases for SRG, in 59% of the cases for CFDA. Our data demonstrate that young leaves take up water from the old ones following both a symplastic and an apoplastic pathway. Water recycling is therefore one of the adaptive responses of these plants allowing them to perform at least a complete growth cycle even during prolonged drought stress periods, using the water stored in the older leaves.

Morphological observations on the co-occurring geophytes Isoetes duriei Bory (Lycophyta, Isoetaceae) and Romulea columnae Sebast. et Mauri (Anthophyta, Iridaceae)

Some preliminary observations on the morphology and leaf anatomy of two geophytes, Isoetes duriei and Romulea columnae, co-occurring in a Mediterranean temporary pond have been reported. The species examined possess characters favourable to the survival of both flooded and arid conditions. The adaptive traits to flooding appear plastic in R. columnae, while I. duriei is “structurally” an aquatic plant. Evolutionary and ecological aspects are briefly discussed.