Secret life of plants: from memory to intelligence.
Plant Signal Behav. 2010 Nov;5(11):1391-4. Epub 2010 Nov 1. PMID: 21051941
Stanislaw Karpiński, Magdalena Szechyńska-Hebda
Plants are able to perform photosynthesis and cannot escape from environmental stresses, so they therefore developed sophisticated, highly responsive and dynamic physiology. Others' and our results indicate that plants solve their optimal light acclimation and immune defenses, photosynthesis and transpiration by a computational algorithm of the cellular automation. Our recent results however suggest that plants are capable of processing information encrypted in light intensity and in its energy. With the help of nonphotochemical quenching and photoelectrophysiological signaling (PEPS) plants are able to perform biological quantum computation and memorize light training in order to optimize their Darwinian fitness. Animals have their network of neuron synapses, electrophysiological circuits and memory, but plants have their network of chloroplasts connected by stromules, PEPS circuits transduced by bundle sheath cells and cellular light memory. It is suggested that plants could be intelligent organisms with much higher organism organization levels than it was thought before.
Article Published Date : Nov 01, 2010
Ornamental indoor plants in hospital rooms enhanced health outcomes of patients recovering from surgery.
J Altern Complement Med. 2009 Sep;15(9):975-80. PMID: 19715461
Seong-Hyun Park, Richard H Mattson
BACKGROUND: Clinical trials have not been reported concerning the health benefits of viewing indoor plants on stress and recovery of surgical patients within a hospital setting. Using various medical and psychologic measurements, this study performed a randomized clinical trial with surgical patients to evaluate whether plants in hospital rooms have therapeutic influences. METHODS: Ninety (90) patients recovering from a hemorrhoidectomy were randomly assigned to either control or plant rooms. With half the patients, live plants were placed in their rooms during postoperative recovery periods. Data collected for each patient included length of hospitalization, analgesics used for postoperative pain control, vital signs, ratings of pain intensity, pain distress, anxiety and fatigue, the State-Trait Anxiety Inventory Form Y-1, the Environmental Assessment Scale, and the Patient's Room Satisfaction Questionnaire. RESULTS: Viewing plants during the recovery period had a positive influence linking directly to health outcomes of surgical patients. Patients in hospital rooms with plants and flowers had significantly more positive physiologic responses evidenced by lower systolic blood pressure, and lower ratings of pain, anxiety, and fatigue than patients in the control room. Patients with plants also felt more positively about their rooms and evaluated them with higher satisfaction when compared with patients in similar rooms without plants. Based on patients' comments, plants brightened up the room environment, reduced stress, and also conveyed positive impressions of hospital employees caring for patients. CONCLUSIONS: Findings of this study confirmed the therapeutic value of plants in the hospital environment as a noninvasive, inexpensive, and effective complementary medicine for surgical patients. Health care professionals and hospital administrators need to consider the use of plants and flowers to enhance healing environments for patients.
Article Published Date : Sep 01, 2009
Biophilia: does visual contact with nature impact on health and well-being?
Int J Environ Res Public Health. 2009 Sep;6(9):2332-43. Epub 2009 Aug 31. PMID: 19826546
Bjørn Grinde, Grete Grindal Patil
It is concluded that an environment devoid of Nature may act as a "discord", i.e., have a negative effect. While the term mismatch is used for any difference between present living conditions and the environment of evolutionary adaptation, discords are mismatches with a potentially undesirable impact on health or quality of life. The problem is partly due to the visual absence of plants, and may be ameliorated by adding elements of Nature, e.g., by creating parks, by offering a view through windows, and by potted plants. The conclusion is based on an evaluation of some fifty relevant empirical studies.
Article Published Date : Sep 01, 2009
Role of phytocystatin in combating metal ion induced conformational alterations in glutathione reductase.
Int J Biol Macromol. 2019 Jan 14;:
Authors: Ahmed A, Shamsi A, Al Shahwan M, Amin F, Bano B
Glutathione reductase (GR) is a flavoprotein that catalyses the reduction of oxidized glutathione (GSSG) to reduced glutathione (2GSH) in the presence of coenzyme NADPH. The importance of glutathione stems from the fact that it serves an important role in various metabolic processes. Plants growing in highly polluted areas are exposed to higher concentration of metal ions; thereby feeling abiotic stress and affecting various regulatory enzyme activities. In this study, effect of metal ions has been studied on GR. Phytocystatins show an increased expression in abiotic stress conditions. Here in, the effect of cystatin isolated from yellow mustard seeds (YMP) on heavy metals induced conformational changes in GR was investigated making use of GR activity assay, UV-absorption spectroscopy, fluorescence spectroscopy, FTIR, CD, ITC and SEM analysis. The results obtained clearly reveals that metal ions like Cu2+ and Zn+2 induces concentration dependent conformational changes in GR; YMP restores these alterations in way decreasing the effective concentration of metal ions.
PMID: 30654031 [PubMed - as supplied by publisher]
[Harmful biological agents in municipal waste thermal treatment plants].
Med Pr. 2018 Dec 18;:
Authors: Cyprowski M
Solid waste storage in specially designated areas - landfills - has been the basic method of municipal solid waste disposal management for many years. However, thermal treatment is the currently preferred method of solid waste disposal. Hygienic assessment of working conditions in municipal waste incineration plants is hindered due to the variability and complexity of pollutants emitted during the combustion process. For many years studies describing this problem have focused mainly on chemical pollution inside the plants as well as emitted into the atmosphere. Available data indicates the presence of organic dust at workplaces in the range 0.1-14 mg/m3. It has been proven that it is a carrier of a wide spectrum of microorganisms, including bacteria, fungi and both mesophilic and thermophilic actinomycetes as well as adenoviruses and torque teno virus (TTV). In the air, at workplaces, bacterial endotoxins have also been found in concentrations reaching even 50 000 EU/m3, which may significantly affect the occurrence of pro-inflammatory reactions in the lungs as well as toxic pneumonitis. Biological agents should be taken into account in the occupational risk assessment for harmful agents present in this environment, and an in-depth characterization of exposure and health effects resulting from contact with these agents should be continued to an even greater extent than before. Med Pr 2019;70(1).
PMID: 30653196 [PubMed - as supplied by publisher]
The Crotalaria juncea metal transporter CjNRAMP1 has a high Fe uptake activity, even in an environment with high Cd contamination.
Int J Phytoremediation. 2019 Jan 17;:1-11
Authors: Nakanishi-Masuno T, Shitan N, Sugiyama A, Takanashi K, Inaba S, Kaneko S, Yazaki K
Large quantities of Fe and Cd accumulate in the leaves of the metal-accumulating leguminous plant, Crotalaria juncea. A member of the metal transporter NRAMP family was cloned from C. juncea. The amino acid sequence of this clone, designated CjNRAMP1, was similar to the sequence of Arabidopsis AtNRAMP1, which is involved in Fe and Cd transport. Organ-specific analysis showed that CjNRAMP1 mRNA was expressed mainly in the leaves of C. juncea plants, as well as in stems and roots. Use of green fluorescent protein fused to CjNRAMP1 suggested its localization to the plasma membranes of plant cells. Complementation experiments using yeast strains with impaired metal transport systems showed that CjNRAMP1 transported both Fe and Cd in an inward direction within the cells. Transgenic Arabidopsis plants overexpressing CjNRAMP1 showed high tolerance to Cd, with Cd translocation from roots to leaves being substantially greater in transgenic than in wild-type plants. Overexpression of CjNRAMP1 resulted in a greater accumulation of Fe in shoots and roots, suggesting that CjNRAMP1 recognizes Fe and Cd as substrates and that the high Cd tolerance of CjNRAMP1 is due to its strong Fe uptake activity, even in the presence of high Cd concentrations in the rhizosphere.
PMID: 30652514 [PubMed - as supplied by publisher]
Hydrogen sulfide (H2 S): A novel component in Arabidopsis peroxisomes which triggers catalase inhibition.
J Integr Plant Biol. 2019 Jan 16;:
Authors: Corpas FJ, Barroso JB, González-Gordo S, Muñoz-Vargas MA, Palma JM
Plant peroxisomes have the capacity to generate different reactive oxygen and nitrogen species (ROS and RNS), such as H2 O2 , superoxide radical (O2 · - ), nitric oxide and peroxynitrite (ONOO- ). These organelles have an active nitro-oxidative metabolism which can be exacerbated by adverse stress conditions. Hydrogen sulfide (H2 S) is a new signaling gasotransmitter caused by the posttranslational modification (PTM) persulfidation. We used Arabidopsis thaliana transgenic seedlings expressing cyan fluorescent protein (CFP) fused to a canonical peroxisome targeting signal 1 (PTS1) to visualize peroxisomes in living cells, as well as a specific fluorescent probe which showed that peroxisomes contain H2 S. H2 S was also detected in chloroplasts under glyphosate-induced oxidative stress conditions. Peroxisomal enzyme activities, including catalase, photorespiratory H2 O2 -generating glycolate oxidase (GOX) and hydroxypyruvate reductase (HPR), were assayed in vitro with a H2 S donor. In line with the persulfidation of this enzyme, catalase activity declined significantly in the presence of the H2 S donor. To corroborate the inhibitory effect of H2 S on catalase activity, we also assayed pure catalase from bovine liver and pepper fruit-enriched samples, in which catalase activity was inhibited. Taken together, these data provide evidence of the presence of H2 S in plant peroxisomes which appears to regulate catalase activity and, consequently, the peroxisomal H2 O2 metabolism.
PMID: 30652411 [PubMed - as supplied by publisher]
Nanophotonics of higher-plant photosynthetic membranes.
Light Sci Appl. 2019;8:5
Authors: Capretti A, Ringsmuth AK, van Velzen JF, Rosnik A, Croce R, Gregorkiewicz T
The thylakoid membrane inside chloroplasts hosts the light-dependent reactions of photosynthesis. Its embedded protein complexes are responsible for light harvesting, excitation energy transfer, charge separation, and transport. In higher plants, when the illumination conditions vary, the membrane adapts its composition and nanoscale morphology, which is characterized by appressed and non-appressed regions known as grana and stroma lamellae, respectively. Here we investigate the nanophotonic regime of light propagation in chloroplasts of higher plants and identify novel mechanisms in the optical response of the thylakoid membrane. Our results indicate that the relative contributions of light scattering and absorption to the overall optical response of grana strongly depend on the concentration of the light-harvesting complexes. For the pigment concentrations typically found in chloroplasts, the two mechanisms have comparable strengths, and their relative value can be tuned by variations in the protein composition or in the granal diameter. Furthermore, we find that collective modes in ensembles of grana significantly increase light absorption at selected wavelengths, even in the presence of moderate biological disorder. Small variations in the granal separation or a large disorder can dismantle this collective response. We propose that chloroplasts use this mechanism as a strategy against dangerously high illumination conditions, triggering a transition to low-absorbing states. We conclude that the morphological separation of the thylakoid membrane in higher plants supports strong nanophotonic effects, which may be used by chloroplasts to regulate light absorption. This adaptive self-organization capability is of interest as a model for novel bioinspired optical materials for artificial photosynthesis, imaging, and sensing.
PMID: 30651980 [PubMed]
Deletion of high-molecular-weight glutenin subunits in wheat significantly reduced dough strength and bread-baking quality.
BMC Plant Biol. 2018 Dec 03;18(1):319
Authors: Zhang Y, Hu M, Liu Q, Sun L, Chen X, Lv L, Liu Y, Jia X, Li H
BACKGROUND: High-molecular-weight glutenin subunits (HMW-GS) play important roles in the elasticity of dough made from wheat. The HMW-GS null line is useful for studying the contribution of HMW-GS to the end-use quality of wheat.
METHODS: In a previous work, we cloned the Glu-1Ebx gene from Thinopyrum bessarabicum and introduced it into the wheat cultivar, Bobwhite. In addition to lines expressing the Glu-1Ebx gene, we also obtained a transgenic line (LH-11) with all the HMW-GS genes silenced. The HMW-GS deletion was stably inherited as a dominant and conformed to Mendel's laws. Expression levels of HMW-GS were determined by RT-PCR and epigenetic changes in methylation patterns and small RNAs were analyzed. Glutenins and gliadins were separated and quantitated by reversed-phase ultra-performance liquid chromatography. Measurement of glutenin macropolymer, and analysis of agronomic traits and end-use quality were also performed.
RESULTS: DNA methylation and the presence of small double-stranded RNA may be the causes of post-transcriptional gene silencing in LH-11. The accumulation rate and final content of glutenin macropolymer (GMP) in LH-11 were significantly lower than in wild-type (WT) Bobwhite. The total protein content was not significantly affected as the total gliadin content increased in LH-11 compared to WT. Deletion of HMW-GS also changed the content of different gliadin fractions. The ratio of ω-gliadin increased, whereas α/β- and γ-gliadins declined in LH-11. The wet gluten content, sedimentation value, development time and stability time of LH-11 were remarkably lower than that of Bobwhite. Bread cannot be made using the flour of LH-11.
CONCLUSIONS: Post-transcriptional gene silencing through epigenetic changes and RNA inhibition appear to be the causes for the gene expression deficiency in the transgenic line LH-11. The silencing of HMW-GW in LH-11 significantly reduced the dough properties, GMP content, wet gluten content, sedimentation value, development time and stability time of flour made from this wheat cultivar. The HMW-GS null line may provide a potential material for biscuit-making because of its low dough strength.
PMID: 30509162 [PubMed - indexed for MEDLINE]
Extracellular biopolymers produced by Dictyosphaerium family - Chemical and immunomodulative properties.
Int J Biol Macromol. 2019 Jan;121:1254-1263
Authors: Halaj M, Paulovičová E, Paulovičová L, Jantová S, Cepák V, Lukavský J, Capek P
Many microalgal species produce a wide range of highly-value products which are interesting for biotechnological applications. Cultivation of microalgal species Dictyosphaerium pulchellum and Dictyosphaerium tetrachotomum, strains Růžicka and Fott resulted yields of 0.2, 0.7 and 1.8 g/L of extracellular biopolymers (EPSs), respectively. All biopolymers were shown to be anionic proteoglycans. The sugar composition analyses of all EPSs showed high contents of hexoses and the presence of partially methylated monosaccharide residues, i.e. hexoses, and deoxy hexoses. The dominant sugar component of all EPSs was found to be galactose. Extracellular microalgal biopolymers were subjected to immunobiological and immunotoxicological evaluation using murine melanoma cancer cells B16, murine fibroblast cell line NIH-3T3, murine macrophages cell line RAW 264.7 and skin construct EpiDerm™ (EPI-200). The EPSs exerted the antiproliferative effectivity; treatment of EPS induced proinflammatory cytokines TNF-α, IL-6, IL-12, IL-1β and IL-17, also engaged in anti-cancer immunity. Immunotoxicological studies revealed their non-toxic character and safe application on EpiDerm™.
PMID: 30342124 [PubMed - indexed for MEDLINE]
Effect of heat root stress and high salinity on glucosinolates metabolism in wild rocket.
J Plant Physiol. 2018 Dec;231:261-270
Authors: Cocetta G, Mishra S, Raffaelli A, Ferrante A
Wild rocket (Diplotaxis tenuifolia L.) is a leafy vegetable appreciated for its characteristic sensory properties which are mainly due to the presence of glucosinolates (GSLs). Short-term exposure to abiotic stresses can induce physiological responses and transcriptional changes which involve GSLs. For this reason, the aim of this work was to study the mechanisms of regulation of GSLs metabolism in rocket subjected to heat stress (40 °C) and high salinity (200 mM NaCl) imposed for up to 48 h. GSLs levels and the expression of methylthioalkylmalate synthase1 (DtMAM1), cytochromeP79F1 (DtCYP79F1), cytochromeP45083A1 (DtCYP83A1), cytosolic-sulfotransferase5b (DtST5b), cytosolic-sulfotransferase5c (DtST5c), flavinmono-oxygenase (DtFMO), myrosinase (DtMyro) and thio-methyl transferase (DtTMT) were analyzed under stress conditions. In addition, the effect on chlorophyll and glucose levels, as well as on chlorophyll a fluorescence were evaluated. Chlorophyll and chlorophyll fluorescence were not affected by the short-term application of stresses. Glucose levels in roots were doubled in response to high salinity, while, in the same organ, GSLs were three fold lower in response to both stresses. The relative content of several aliphatic GSLs was significantly reduced in leaves as a response to both stresses. A key role in GSLs metabolism and in the response to salinity is hypothesized for the gene DtTMT, as it showed an increment in transcripts accumulation (three-fold) consistent with the decrement in the GSLs levels found in salt-exposed leaves and roots. The results obtained in this study can be used in breeding programmes aiming to enhance rocket sensory quality and to improve the resistance to abiotic stresses.
PMID: 30326419 [PubMed - indexed for MEDLINE]
Negative Air Ions and Their Effects on Human Health and Air Quality Improvement.
Int J Mol Sci. 2018 Sep 28;19(10):
Authors: Jiang SY, Ma A, Ramachandran S
Negative air ions (NAIs) have been discovered for more than 100 years and are widely used for air cleaning. Here, we have carried out a comprehensive reviewing on the effects of NAIs on humans/animals, and microorganisms, and plant development. The presence of NAIs is credited for increasing psychological health, productivity, and overall well-being but without consistent or reliable evidence in therapeutic effects and with controversy in anti-microorganisms. Reports also showed that NAIs could help people in relieving symptoms of allergies to dust, mold spores, and other allergens. Particulate matter (PM) is a major air pollutant that affects human health. Experimental data showed that NAIs could be used to high-efficiently remove PM. Finally, we have reviewed the plant-based NAI release system under the pulsed electric field (PEF) stimulation. This is a new NAI generation system which releases a huge amount of NAIs under the PEF treatment. The system may be used to freshen indoor air and reduce PM concentration in addition to enriching oxygen content and indoor decoration at home, school, hospital, airport, and other indoor areas.
PMID: 30274196 [PubMed - indexed for MEDLINE]
Potential of aquatic oomycete as a novel feedstock for microbial oil grown on waste sugarcane bagasse.
Environ Sci Pollut Res Int. 2018 Nov;25(33):33443-33454
Authors: Patel A, Matsakas L, Pruthi PA, Pruthi V
Biodiesel production from vegetable oils is not sustainable and economical due to the food crisis worldwide. The development of a cost-effective non-edible feedstock is essential. In this study, we proposed to use aquatic oomycetes for microbial oils, which are cellulolytic fungus-like filamentous eukaryotic microorganisms, commonly known as water molds. They differ from true fungi as cellulose is present in their cell wall and chitin is absent. They show parasitic as well as saprophytic nature and have great potential to utilize decaying animal and plant debris in freshwater habitats. To study the triacylglycerol (TAG) accumulation in the aquatic oomycetes, the isolated water mold Achlya diffusa was cultivated under semi-solid-state conditions on waste sugarcane bagasse, which was compared with the cultivation in Czapek (DOX) medium. A. diffusa grown on waste sugarcane bagasse showed large lipid droplets in its cellular compartment and synthesized 124.03 ± 1.93 mg/gds cell dry weight with 50.26 ± 1.76% w/w lipid content. The cell dry weight and lipid content of this water mold decreased to 89.54 ± 1.21 mg/gds and 38.82% w/w, respectively, when cultivated on standard medium Czapek-Dox agar (CDA). For the fatty acid profile of A. diffusa grown in sugarcane bagasse and CDA, in situ transesterification (IST) and indirect transesterification (IDT) approaches were evaluated. The lipid profile of this mold revealed the presence of C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, C20:0, and C21:0 fatty acids, which is similar to vegetable oils. The biodiesel properties of the lipids obtained from A. diffusa satisfied the limits as determined by international standards ASTM-D6751 and EN-14214 demonstrating its suitability as a fuel for diesel engines.
PMID: 30264348 [PubMed - indexed for MEDLINE]
Bufadienolides from Kalanchoe daigremontiana modulate the enzymatic activity of plasmin - In vitro and in silico analyses.
Int J Biol Macromol. 2018 Dec;120(Pt B):1591-1600
Authors: Kolodziejczyk-Czepas J, Pasiński B, Ponczek MB, Moniuszko-Szajwaj B, Kowalczyk M, Pecio Ł, Nowak P, Stochmal A
Plasmin (EC 22.214.171.124) is a key enzyme of the fibrinolytic system, responsible for the degradation of fibrin clot and maintaining blood fluidity. Hence, alterations of the fibrinolytic capacity of blood plasma may contribute to thrombotic or bleeding complications. The aim of this study was to determine effects of a bufadienolide-rich fraction, isolated from roots of Kalanchoe daigremontiana (0.05-50 μg/ml) on enzymatic properties of plasmin. Hydrolysis of a synthetic substrate S-2251 (H-D-Valyl-l-leucyl-l-lysine-p-nitroaniline dihydrochloride) by plasmin revealed that the bufadienolide-rich fraction had a diverse effect on this enzyme, dependently on the concentration range. While the lower concentrations of the examined fraction (0.05-2.5 μg/ml) significantly enhanced the amidolytic activity of plasmin, at 25-50 μg/ml concentrations, the enzyme was evidently inhibited (by about 60%). The Lineweaver-Burk plot indicated on an uncompetitive inhibition of plasmin. Inhibitory effects (up to 80%) were also found in the streptokinase-induced plasminogen activation to plasmin. Docking results suggest that only some of compounds (mostly bersaldegenin 1-acetate (10), bryotoxin (13) and hovetrichoside C (17)) were bound to plasminogen/plasmin, depending on the presence or absence of the substrate in the active site. The obtained findings suggest allosteric regulation of plasminogen activation and plasmin activity by components of the examined fraction.
PMID: 30261260 [PubMed - indexed for MEDLINE]
The Availability and Nutritional Adequacy of Gluten-Free Bread and Pasta.
Nutrients. 2018 Sep 25;10(10):
Authors: Allen B, Orfila C
Management of coeliac disease (CD) requires the removal of gluten from the diet. Evidence of the availability, cost, and nutritional adequacy of gluten-free (GF) bread and pasta products is limited. GF flours are exempt from UK legislation that requires micronutrient fortification of white wheat flour. This study surveyed the number and cost of bread and pasta products available and evaluated the back-of-pack nutritional information, the ingredient content, and the presence of fortification nutrients of GF bread and pasta, compared to standard gluten-containing equivalent products. Product information was collected from four supermarket websites. Standard products were significantly cheaper, with more products available than GF (p < 0.05). GF bread products were significantly higher in fat and fiber (p < 0.05). All GF products were lower in protein than standard products (p < 0.01). Only 5% of GF breads were fortified with all four mandatory fortification nutrients (calcium, iron, niacin, and thiamin), 28% of GF breads were fortified with calcium and iron only. This lack of fortification may increase the risk of micronutrient deficiency in coeliac sufferers. It is recommended that fortification legislation is extended to include all GF products, in addition to increased regulation of the nutritional content of GF foods.
PMID: 30257431 [PubMed - indexed for MEDLINE]
Interactions between whey protein or polymerized whey protein and soybean lecithin in model system.
J Dairy Sci. 2018 Nov;101(11):9680-9692
Authors: Sun XM, Wang CN, Guo MR
Soybean lecithin is often used as a surfactant in food formulation. The aim of this study was to investigate the interactions between soybean lecithin (SL, 0-3%, wt/vol) and whey protein (WP, 10%, wt/vol) or polymerized whey protein (PWP, 10%, wt/vol) induced by heating WP solutions at 85°C for 0 to 20 min at pH 7.0. The samples were evaluated for zeta potential, particle size, morphology, rheological properties, thermal properties, secondary structure, and surface hydrophobicity. Zeta potential of WP increased linearly as SL level increased from 0 to 3%, whereas that of PWP changed with plateau at SL level of 1%, which may be due to the aggregation of SL. The addition of SL increased the particle size and apparent viscosity of both WP and PWP. All the samples exhibited different morphology depending on SL level and heating time according to transmission electron microscopy images. Whey protein showed obviously decreased gelation time and increased storage modulus in the presence of SL. Differential scanning calorimetry curves confirmed the effects of SL on the thermal properties of both WP and PWP. Circular dichroism spectra indicated that SL had effects on the secondary structure of both WP and PWP. The changes in surface hydrophobicity indicated the hydrophobic interactions between WP/PWP and SL. Data indicate that the physicochemical and functional properties of WP and PWP can be altered by adding soybean lecithin.
PMID: 30197146 [PubMed - indexed for MEDLINE]
First description of extrafloral nectaries in Opuntia robusta (Cactaceae): Anatomy and ultrastructure.
PLoS One. 2018;13(7):e0200422
Authors: Sandoval-Molina MA, Zavaleta-Mancera HA, León-Solano HJ, Solache-Ramos LT, Jenner B, Morales-Rodríguez S, Patrón-Soberano A, Janczur MK
To our knowledge, there are no studies about the structure and ecological function of extrafloral nectaries (EFNs) in Opuntia robusta. This is the first description of EFNs in O. robusta, where young spines have an interesting structure and a secreting function, which are different from EFNs described in other Cactaceae species. We used light, scanning-electron, and transmission-electron microscopy to examine morphology, anatomy, and ultrastructure of the secretory spines in areoles in female and hermaphrodite individuals of O. robusta. Young cladodes develop areoles with modified and secretory spines as EFNs only active during the early growth phase. EFNs are non-vascularized structures, with no stomata, that consist of a basal meristematic tissue, a middle elongation region, and an apical secretory cone formed by large globular epidermal cells, containing nectar and medullar elongated cells. We observed the presence of Golgi apparatus, vesicles and plastids in the medullar and sup-epidermal cells of the spine. We propose that the nectar is stored in the globular cells at the apex of the spine and secreted by breaking through the globular cells or by pores. We recorded a more frequent presence of ants on younger cladode sprouts producing young secreting spines: this result is parallel with the predictions of Optimal Defense Hypothesis, which states that younger plant organs should be better defended than older ones because their loss produces a higher fitness impairment. Although Diaz-Castelazo's hypothesis states that a more complex structure of EFNs correlates with their lower among-organs dispersion, comparing to less complex EFNs, non-vascularized structure of EFNs in O. robusta is not associated with their higher among-organs dispersion likened to O. stricta, which produces vascularized EFNs. We provide evidence that this characteristic is not a good taxonomic feature of Opuntia genus. Moreover, the comparison of EFNs of O. robusta and O. stricta suggests that the hypothesis of Diaz-Castelazo should be revised: it is rather a rule but not a law.
PMID: 30016339 [PubMed - indexed for MEDLINE]