Non-photosynthetic Pigments Research Articles

Exploring Leaf Anthocyanin Concentrations and Light Effects on Lettuce Growth

Anthocyanins are secondary metabolites classified as water-soluble, non-photosynthetic pigments with the potential ability to shield chloroplasts from excess light energy. This study investigated the morphological and physiological responses of six lettuce (Lactuca sativa) cultivars with different leaf anthocyanin contents grown in a greenhouse under different supplemental photosynthetic photon flux densities (PPFD). Cultivars ‘Cherokee’, ‘Teodore’, ‘Rex’, and ‘Rouxai’ decreased in specific leaf area with increasing PPFD, respectively. We observed that growth in cultivars with higher leaf anthocyanin content (‘Cherokee’ and ‘Rouxai’) increased with increasing PPFD. Light use efficiency (LUE) is an important physiological parameter affecting biomass accumulation, and cultivars ‘Cherokee’, ‘Rex’, ‘Teodore’, and ‘Rouxai’ had the highest LUE and shoot weight. We found that red lettuce varieties, especially ‘Cherokee’ and ‘Rouxai’, showed increased shoot dry weight as light intensity increased. Interestingly, these varieties also had the highest anthocyanin levels in their leaves. This suggests that higher anthocyanin content might contribute to the increased shoot dry weight under higher light intensity, although this was mainly evident in ‘Cherokee’.

Detectability of Surface Biosignatures for Directly Imaged Rocky Exoplanets.

Modeling the detection of life has never been more opportune. With next-generation space telescopes, such as the currently developing Habitable Worlds Observatory (HWO) concept, we will begin to characterize rocky exoplanets potentially similar to Earth. However, few realistic planetary spectra containing surface biosignatures have been paired with direct imaging telescope instrument models. Therefore, we use a HWO instrument noise model to assess the detection of surface biosignatures affiliated with oxygenic, anoxygenic, and nonphotosynthetic extremophiles. We pair the HWO telescope model to a one-dimensional radiative transfer model to estimate the required exposure times necessary for detecting each biosignature on planets with global microbial coverage and varying atmospheric water vapor concentrations. For modeled planets with 0-50% cloud coverage, we determine pigments and the red edge could be detected within 1000 hr (100 hr) at distances within 15 pc (11 pc). However, tighter telescope inner working angles (2.5 λ/D) would allow surface biosignature detection at further distances. Anoxygenic photosynthetic biosignatures could also be more easily detectable than nonphotosynthetic pigments and the photosynthetic red edge when compared against a false positive iron oxide slope. Future life detection missions should evaluate the influence of false positives on the detection of multiple surface biosignatures.

The role of supplemental lighting during late fall and winter on photosynthetic and non-photosynthetic pigments biosynthesis of cut rose flower (Rosa hybrida cv. ‘Dolce Vita’)

ABSTRACT Low levels of natural light within the late fall and winter periods are main restricting factors for greenhouse-cut rose flower production in northern countries. Here, the effects of supplemental lighting on photosynthetic and non-photosynthetic pigments and the morphological response of cut rose flower cv. ‘Dolce Vita’ were investigated. Four different supplemental lighting regimes, including 85, 170, 255, and 340 μmol·m−2·s−1 PPFD using a high-pressure sodium lamp for a six-hour day extension started at sunset were applied to rose plants during late fall and winter. With increasing light intensity to 255 μmol·m−2·s−1 PPFD, the content of chlorophyll a, total chlorophyll, carotenoid content, and the ratio of chlorophylls a/b as well as amount of anthocyanins greatly improved. The highest phenol content and total antioxidant capacity was observed in 170 μmol·m−2·s−1 PPFD. Moreover, extending of daylength by light intensity of 255 μmol·m−2·s−1 PPFD had a significant affirmative effect on traits of growth, including flower stem length (P < 0.01), leaf number (P < 0.05), renewal bud formation (P < 0.05), time of harvesting (P < 0.05), and vase life of cut flowers (P < 0.01). Considering physiological and morphological improvement, extending of daylength from 10-h to 16-h by supplemental light of 255 μmol·m−2·s−1 PPFD would be the best choice to cultivate cut rose flower cv. ‘Dolce Vita’.

Effect of Abnormal Light/Dark Cycles on the Pigment Complex of Brassicaceae and Solanaceae Plants

Under controlled environmental conditions, the authors studied the effect of extendedlight/dark cycles of 24/12, 48/24, 96/48, and 120/60 h and continuous lighting on the content and ratio ofphotosynthetic and nonphotosynthetic pigments in a number of Solanaceae (eggplant (Solanum melongena L.),sweet pepper (Capsicum annuum L.), tobacco (Nicotiana tabacum L.), and tomato (Solanum lycopersicum L.))and Brassicaceae (broccoli (Brassica oleracea var. italica Plenck), mizuna (Brassica rapa ssp nipposinica(L.H. Bailey) Hanelt), arugula (Eruca vesicaria sp. sativa Mill.), and cauliflower (Brassica oleracea L. var.botrytis L.)) plants. Plants were grown in controlled-climate chambers at 23°С and light intencity of270 μmol/(m2s) PAR. Control plants were grown under photoperiod of 16/8 h. Continuous lightingdecreased the content of chlorophyll, its share in light-harvesting complex and chlorophyll to carotenoidsratio, but increased chlorophyll a/b ratio and the content of anthocyanins and flavonoids; these effects weredifferently manifested depending on plant species. At all other examined light/dark cycles (24/12, 48/24,96/48, and 120/60 h) where average daily light integral did not differ from such under common photoperiod(16/8 h), changes in pigment complex were often observed similar to photoprotective reactions occurringupon exposure of plants to excess illumination (a decrease in the content of photosynthetic pigments, modification of their ratios, and accumulation of protective, nonphotosynthetic pigments). At the same time,plant responses were species-specific. On the whole, the obtained results have shown that changes within theplant pigment complex may be induced not only by excessive light energy coming to plants, but also by distribution of daily light integral in time as it occurs in response to abnormal light/dark cycles that, in theauthors’ opinion, cause a circadian asynchrony

Influence of the phytoplankton community composition on the in situ fluorescence signal: Implication for an improved estimation of the chlorophyll-a concentration from BioGeoChemical-Argo profiling floats

In-situ fluorescence is a widely used method to estimate the chlorophyll-a (Chla) concentration, a proxy of the phytoplankton biomass. With the emergence of autonomous platforms such as BioGeoChemical-Argo (BGC-Argo) profiling floats, its use has expanded to global scale observations. However, the relationship between in-situ fluorescence and Chla may vary significantly, leading to major discrepancies between oceanic regions. This study aims to investigate the main sources of the natural variability in the in-situ fluorescence signal in the global open ocean, specifically the influence of the phytoplankton community composition. In this view, we analyzed a combination of three datasets comprising concomitant measurements of in-situ fluorescence, pigment concentrations and phytoplankton absorption spectra. Two datasets cover several contrasted bioregions of the global ocean whereas the third one consists of a regional time series in the northwestern Mediterranean Sea, which allows to examine the effect of phytoplankton community composition on the fluorescence signal on the global, seasonal and vertical scales. We studied the variability of the two major drivers of the natural variability of the fluorescence process, i.e. the light absorption and the fluorescence quantum yield of phytoplankton, in regards of the variability of the pigment composition of the communities. The community composition correlates substantially with the Chla-to-fluorescence ratio, with high fluorescence values associated with phytoplankton communities dominated by large cells. This trend may be explained by the combined effects of the community composition on the phytoplankton absorption coefficient and the fluorescence quantum yield, and is consistently observed globally, seasonally and vertically. Non-photosynthetic pigments also appear to play a critical role in oligotrophic surface waters, leading to a reduction of the quantum yield of fluorescence. The results indicate that the phytoplankton community composition plays a key role in the relationship between the in-situ fluorescence signal and Chla concentration. Therefore, we suggest that taking into account the composition of phytoplankton communities in the retrieval of the Chla concentration from current in-situ fluorometers, those mounted on BGC-Argo floats in particular, would lead to a better estimation of the phytoplankton biomass on a wide range of spatial and temporal scales.

Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their "Antioxidant" Function Prominent in Leaves Exposed to Severe Summer Drought?

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate.

Molecular Bases of Fruit Quality in Prunus Species: An Integrated Genomic, Transcriptomic, and Metabolic Review with a Breeding Perspective.

In plants, fruit ripening is a coordinated developmental process that requires the change in expression of hundreds to thousands of genes to modify many biochemical and physiological signal cascades such as carbohydrate and organic acid metabolism, cell wall restructuring, ethylene production, stress response, and organoleptic compound formation. In Prunus species (including peaches, apricots, plums, and cherries), fruit ripening leads to the breakdown of complex carbohydrates into sugars, fruit firmness reductions (softening by cell wall degradation and cuticle properties alteration), color changes (loss of green color by chlorophylls degradation and increase in non-photosynthetic pigments like anthocyanins and carotenoids), acidity decreases, and aroma increases (the production and release of organic volatile compounds). Actually, the level of information of molecular events at the transcriptional, biochemical, hormonal, and metabolite levels underlying ripening in Prunus fruits has increased considerably. However, we still poorly understand the molecular switch that occurs during the transition from unripe to ripe fruits. The objective of this review was to analyze of the molecular bases of fruit quality in Prunus species through an integrated metabolic, genomic, transcriptomic, and epigenetic approach to better understand the molecular switch involved in the ripening process with important consequences from a breeding point of view.

Characterization of Exogenous Nitric Oxide Effect on Crocus sativus Response to Different Irrigation Regimes

Water scarcity is one of the main factors limiting crop production worldwide. The study on response of saffron to irrigation regime showed that one-time irrigation at field capacity of 100% resulted in the greatest number and weight of flower, and dry stigma yield, but weekly irrigation regime at the same conditions prevented flowering process. One-time irrigation regime reduced water potential (Ψw) of plants, while the contents of chlorophylls, carotenoid, anthocyanin, carbohydrates, phenol, amino acid, proline, H2O2, and the activity of antioxidant enzymes in the one-time irrigated plants were higher than in the weekly irrigated plants. The nitric oxide (NO) donor, sodium nitroprusside (SNP), significantly increased photosynthetic and non-photosynthetic pigments, metabolites, and antioxidants in both irrigation regimes, with the highest content in the one-time irrigated plants. The SNP treatment increased the flower yield in the one-time irrigated plants, but it could not induce flowering in the weekly irrigated plants. Collectively, these results demonstrated the importance of irrigation regime in flower induction in saffron. Even though the exogenous SNP improved the performance of saffron, it could not overcome the importance of irrigation frequency regime on flowering process. Overall, the SNP application accompanied with the one-time irrigation regime provided higher flower yield and improved the physiological performance of saffron plant.

Relative effectiveness of ethylenediurea, phenyl urea, ascorbic acid and urea in preventing groundnut (Arachis hypogaea L) crop from ground level ozone

Abstract Tropical countries including India worried for loss of agricultural productivity and food security due to greater risk of meteorological conditions. Additionally, enhanced tropospheric ozone of these countries further affected agricultural productivity. Thus, adapting to a new strategy to protect the crops from ozone is an imperative task. Ethylene diurea (EDU) is most effective protectant and popular among the researchers to assess the ozone related plant loss. While, phenyl urea (PU) and ascorbic acid (AA) are known for their role in plants antioxidative system and urea (U) is used for quick nitrogen supply to plants, although, their effectiveness under ozone pollution is merely known. A field study was conducted to assess the relative effectiveness of EDU, PU, AA and U on growth and productivity of groundnut (Arachis hypogaea L var. GG-20) under ozone stress. Result of the study showed increased photosynthetic and non-photosynthetic pigments in protectant applied plants than the plant without any protectant. Primary metabolites, growth and development were also higher in plants under protectant application. Highest growth was observed in plants treated with EDU followed by PU > AA > U than control plants. Antioxidant ascorbic acid concentration was also high in EDU followed by PU > AA > U and control while, phenol contents showed the trend reverse to ascorbic acid and found least under EDU treatment. Application of EDU increased 30.45% of groundnut yield while, increase in yield under PU, AA and U was 18.39%, 10.91% and 2.58% than control, respectively. Study concluded EDU as the most effective protectant for ozone stress while, plant response under PU treatment is close to EDU for most of the parameters. AA showed moderate protective nature and U showed the least protection. Therefore, presented study clarified that PU can be used as most suitable alternative of EDU for protection of plants from ozone pollution.

UV-B Physiological Changes Under Conditions of Distress and Eustress in Sweet Basil.

UV-B radiation has been previously reported to induce protective or deleterious effects on plants depending on the UV-B irradiation doses. To elucidate how these contrasting events are physiologically coordinated, we exposed sweet basil plants to two UV-B doses: low (8.5 kJ m−2 day−1, 30 min exposure) and high (68 kJ m−2 day−1, 4 h exposure), with the plants given both doses once continuously in a single day. Physiological tests during and after both UV-B exposures were performed by comparing the stress-induced damage and adverse effects on photosynthetic activity, the concentration and composition of photosynthetic and non-photosynthetic pigments, and stress-related hormones biosynthesis in basil plants. Our results showed that upon receiving a high UV-B dose, a severe inactivation of oxygen evolving complex (OEC) activity at the PSII donor side and irreversible PSII photodamage caused primarily by limitation of the acceptor side occurred, which overloaded protective mechanisms and finally led to the death of the plants. In contrast, low UV-B levels did not induce any signs of UV-B stress injuries. The OEC partial limitation and the inactivation of the electron transport chain allowed the activation of photoprotective mechanisms, avoiding irreversible damage to PSII. Overall results indicate the importance of a specific response mechanisms regulating photoprotection vs irreversible photoinhibition in basil that were modulated depending on the UV-B doses.

Modeling Photoprotection at Global Scale: The Relative Role of Nonphotosynthetic Pigments, Physiological State, and Species Composition

AbstractMicroalgae are capable of acclimating to dynamic light environments, as they have developed mechanisms to optimize light harvesting and photosynthetic electron transport. When absorption of light exceeds photosynthetic capacity, various physiological protective mechanisms prevent damage of the photosynthetic apparatus. Xanthophyll pigments provide one of the most important photoprotective mechanisms to dissipate the excess light energy and prevent photoinhibition. In this study, we coupled a mechanistic model for phytoplankton photoinhibition with the global biogeochemical model Regulated Ecosystem Model version 2. The assumption that photoinhibition is small in phytoplankton communities acclimated to ambient light allowed us to predict the photoprotective needs of phytoplankton. When comparing the predicted photoprotective needs to observations of pigment content determined by high‐performance liquid chromatography, our results showed that photoprotective response seems to be mediated in most parts of the ocean by a variable ratio of xanthophyll pigments to chlorophyll. The variability in the ratio appeared to be mainly driven by changes in phytoplankton community composition. Exceptions appeared at high latitudes where other energy dissipating mechanisms seem to play a role in photoprotection and both taxonomic changes and physiological acclimation determine community pigment signature. Understanding the variability of community pigment signature is crucial for modeling the coupling of light absorption to carbon fixation in the ocean. Insights about how much of this variability is attributable to changes in community composition may allow us to improve the match between remotely sensed optical data and the underlying phytoplankton community.

Cast adrift: Physiology and dispersal of benthic Sargassum spinuligerum in surface rafts

AbstractConnectivity of populations through the transfer of individuals is one of the key processes for maintaining ecosystem stability and resilience of coastal ecosystems. During reproduction, dislodged seaweeds of the genus Sargassum form large pelagic surface rafts that can persist for several weeks, and potentially act as a dispersal vector. In surface rafts, seaweeds are rapidly exposed to increased light, elevated temperatures, and altered hydrodynamic conditions. Acclimation to surface conditions is necessary for survival during the rafting phase, but there is limited knowledge of seaweed physiology in rafts. To understand the mechanisms for acclimation, we created rafts of floating Sargassum spinuligerum for 2 weeks and compared these experimental fronds to those attached to the seafloor. We measured nutrients, photosynthetic and nonphotosynthetic pigments, and phlorotannins to investigate their role in the persistence of mature Sargassum at the ocean surface as indicated by photosynthetic rates and reproductive status. We also studied potential surface movement of the rafted seaweed over 3‐weeks of particle tracking using an existing oceanographic model. Photosynthesis and reproductive status were similar between benthic and rafted seaweeds, indicating no change to overall metabolic processes during rafting. While phlorotannin concentrations and photosynthetic pigments were unchanged, photoprotective xanthophyll pigments were more abundant in rafted individuals, suggesting acclimation to surface light conditions. Our results suggest that, in the short term, S. spinuligerum employ chemical strategies to acclimate and maintain physiological processes in the rafting environment and potentially fix more carbon, allowing these rafts to act as dispersal vectors among populations over tens of kilometers apart.

ОСОБЕННОСТИ НАКОПЛЕНИЯ ФЕНОЛЬНЫХ СОЕДИНЕНИЙ В РАСТЕНИЯХ НЕКОТОРЫХ ВИДОВ РОДА RUMEX L.

One of the main tasks of modern pharmacognosy is the screening of novel natural sources of bioactive compounds with a view to discovering new drugs. Of particular interest are plants of the genus sorrel (Rumex L.), which are containing various phytochemical compounds and therefore have a wide range of biological and medicinal activities. The phonological features of accumulation of phenolic compounds (total phenolic compounds, catechins, leucoanthocyanins, and anthocyanins) by two dominant species of sorrel in meadow phytocenoses of Kaliningrad region: curly dock (Rumex crispus L.) and bitter dock (Rumex obtusifolius L.) were studied. The content of phenolic compounds in different plant parts (stem, stem and basal leaves, roots, and inflorescences) during flowering and fruiting by spectrophotometric method (Shimadzu UV3600, Japan) were investigated. The species characteristic in the accumulation of different phenolic compounds groups was identified. It was shown the maximal content of phenolic compounds in R. crispus and in R. obtusifolius was during flowering. The species specificity consisted in higher total phenolic compounds content in stem leaves and in reproductive organs and in higher anthocyanins content in the all investigated parts of R. crispus compared with R. obtusifolius.The maximal content of polyphenols in roots and high level of catechins in roots, leaves and in nflorescences by R. obtusifolius were during flowering. The biological feature of this specie consists in active accumulation of leucoanthocyanins in the basal leaves during fruiting. It was shown relatively low level of accumulation of non-photosynthetic pigments of phenolic nature – anthocyanins. The level of anthocyanins in vegetative and reproductive organs of studied sorrel species was lower as level of flavan-3,4-diols. The level of catechins in the tissues of R. crispus and R. obtusifolius was significantly higher than the content of flavan-3,4-diols.

Economic maximization of alfalfa medically-active phytoconstituents

Medicinal plants are leading source of phytochemicals. A pot experiment was designed to evaluate the effect of various water regimes (33, 67 and 100% watering) on the ability of alfalfa plants grown in soils with different texture (33, 67 and 100% sand) to synthesize phenolics, non-photosynthetic pigments, vitamins and minerals. Under drought, the amount of total phenols, saponins, tannins, flavonoids and alkaloids increased with the maximum content of total phenols, tannins and flavonoids recorded for plants in soil with 67% sand. For saponins, 33% sand caused the highest values, while alkaloids increased with increasing sand proportion. Water stress also increased the amount of anthocyanins, lycopene and β-carotene. With adequate irrigation, soil with 33% sand caused the highest amount of these pigments while under drought; their values fluctuated among the three soil types. Moreover, the amount of vitamin C, B1 and B2 increased under water deficit; and their amount increased with increasing sand. Furthermore, the amount of sodium, potassium and calcium increased with drought; while the reverse was recorded for magnesium and phosphorus with the maximum titers of all the addressed elements in plants grown in 100% sand. Thence, little water availability may be an efficient technique invigorating alfalfa medicinal efficacy.

Photosynthetic parameters in the northern South China Sea in relation to phytoplankton community structure

AbstractMany recent models for retrieval of primary production in the sea from ocean‐color data are temperature based. But previous studies in low latitudes have shown that models that include phytoplankton community structure can have improved predictive capability. In this study, we measured photosynthetic parameters from photosynthesis‐irradiance (P‐E) experiments, phytoplankton absorption coefficients, and phytoplankton community structure derived from algal pigments during four cruises in the northern South China Sea (NSCS). The maximum quantum yield of CO2 ( ) and the chlorophyll a‐normalized P‐E curve light‐limited slope (αB) varied significantly with the blue‐to‐red ratio of phytoplankton absorption peaks (aph(435)/aph(676)) (p &lt; 0.001, r = −0.459 and −0.332, respectively). The unexplained variability could be due in part to the absorption associated with nonphotosynthetic pigments. The chlorophyll a‐normalized light‐saturated photosynthetic rate ( ) at the surface showed a unimodal distribution over the chlorophyll a range during the spring and summer, and significantly increased when Prochlorococcus was outcompeted by other picophytoplankton (p &lt; 0.01). Almost 60% of the variance of could be explained by a piecewise regression with phytoplankton absorption coefficients and pigment markers. Unlike previous studies, our data showed that changes of were unrelated to the size structure of phytoplankton. Although a temperature‐based approach could not effectively predict αB and in the NSCS, a trophic‐based approach can be used for assignment of these parameters in a regional primary production model using ocean‐color data.

Nonphotosynthetic pigments as potential biosignatures.

Previous work on possible surface reflectance biosignatures for Earth-like planets has typically focused on analogues to spectral features produced by photosynthetic organisms on Earth, such as the vegetation red edge. Although oxygenic photosynthesis, facilitated by pigments evolved to capture photons, is the dominant metabolism on our planet, pigmentation has evolved for multiple purposes to adapt organisms to their environment. We present an interdisciplinary study of the diversity and detectability of nonphotosynthetic pigments as biosignatures, which includes a description of environments that host nonphotosynthetic biologically pigmented surfaces, and a lab-based experimental analysis of the spectral and broadband color diversity of pigmented organisms on Earth. We test the utility of broadband color to distinguish between Earth-like planets with significant coverage of nonphotosynthetic pigments and those with photosynthetic or nonbiological surfaces, using both 1-D and 3-D spectral models. We demonstrate that, given sufficient surface coverage, nonphotosynthetic pigments could significantly impact the disk-averaged spectrum of a planet. However, we find that due to the possible diversity of organisms and environments, and the confounding effects of the atmosphere and clouds, determination of substantial coverage by biologically produced pigments would be difficult with broadband colors alone and would likely require spectrally resolved data. Key Words: Biosignatures—Exoplanets—Halophiles—Pigmentation—Reflectance spectroscopy—Spectral models. Astrobiology 15, 341–361.

Accounting for the decrease of photosystem photochemical efficiency with increasing irradiance to estimate quantum yield of leaf photosynthesis.

Maximum quantum yield for leaf CO2 assimilation under limiting light conditions (Φ CO2LL) is commonly estimated as the slope of the linear regression of net photosynthetic rate against absorbed irradiance over a range of low-irradiance conditions. Methodological errors associated with this estimation have often been attributed either to light absorptance by non-photosynthetic pigments or to some data points being beyond the linear range of the irradiance response, both causing an underestimation of Φ CO2LL. We demonstrate here that a decrease in photosystem (PS) photochemical efficiency with increasing irradiance, even at very low levels, is another source of error that causes a systematic underestimation of Φ CO2LL. A model method accounting for this error was developed, and was used to estimate Φ CO2LL from simultaneous measurements of gas exchange and chlorophyll fluorescence on leaves using various combinations of species, CO2, O2, or leaf temperature levels. The conventional linear regression method under-estimated Φ CO2LL by ca. 10-15%. Differences in the estimated Φ CO2LL among measurement conditions were generally accounted for by different levels of photorespiration as described by the Farquhar-von Caemmerer-Berry model. However, our data revealed that the temperature dependence of PSII photochemical efficiency under low light was an additional factor that should be accounted for in the model.

A Positive Response of UV-B (280–320 nm) Enhanced Solar Radiation on the Growth and Physiological Activities of Mint (Mentha arvensisL.)

The changes in plant morphology, foliar characteristics and physiological parameters were studied in Menthaarvensis, an aromatic herb grown under UV-B (ultraviolet-B (280-320nm)) enhanced solar radiation (simulated to 6–24% O3 (ozone) depletion). UV-B enhancement was found to induce positive photomorphogenetic changes by increasing the fresh and dry weights. The SEM (scanning electron microscope) analysis of abaxial and adaxial leaf surfaces showed more oil glands with high stomatal frequency under enhanced UV-B when compared with ambient control. On unit fresh weight basis, Chl (chlorophyll) a and b and total Chl were enhanced in addition to the non-photosynthetic pigments such as flavonoids and anthocyanins. Measurement of photosynthetic efficiency in terms of fluorescence induction kinetics confirms that an alteration or redistribution of photosystems had occurred in Mentha offering resistance against UV-B. On the whole, a positive response at the level of morphology and physiological parameters was observed in Mentha seedlings grown under UV-B enhanced solar radiation.

Betalain Color Morphs Exhibit Differential Growth, Defensive Ability, and Pollen Tube Growth Rates inMirabilis jalapa(Nyctaginaceae)

Premise of research. Nonphotosynthetic pigments play significant roles in plant life history, including in pigmentation, pollinator attraction, antioxidants, and defense against pathogens and herbivores. However, little is known about the specific roles of the betalains, which are present in several families of the Caryophyllales. In this study, we took a phenotypic and experimental approach to investigate whether betalain pigments might play diverse roles in plant life history as their phylogenetic counterparts, the anthocyanins, do.Methodology. We measured floral and leaf betalain concentrations and several phenological and performance traits in four floral color morphs of horticultural lines of Mirabilis jalapa (Nyctaginaceae). We also performed herbivore assays and measured pollen tube length in situ to investigate the role of betalain concentration in defense and prezygotic barriers among the floral color morphs.Pivotal results. Our results show that betacyanin and betaxanthin concentrations in leaves are negatively associated with leaf damage by a generalist herbivore and that pollen performance is associated with betacyanin and betaxanthin levels in the donor or recipient flowers. We also suggest that the floral color morphs significantly differ with respect to phenotypic architecture, with the pink morphs being slightly larger but germinating later than the other color morphs.Conclusions. Our experiments using these horticultural lines suggest that betalains and resulting floral color morphs of M. jalapa are associated with several plant life-history traits, such as growth rate, germination, defense against herbivory, and pollination success. It is likely that these roles are subject to selection, and further studies should be conducted along these lines.

Effects of ascorbic acid and gibberellin A3 on alleviation of salt stress in common bean (Phaseolus vulgaris L.) seedlings

Salinity, a severe environmental factor, has limited the growth and productivity of crops. Many compounds have been applied to minimize the harmful effects of salt stress on plant growth. An experiment was conducted to investigate the interactive effects of exogenous ascorbic acid (AsA) and gibberellic acid (GA3) on common bean (Phaseolus vulgaris L. cv. Naz) seedlings under salt stress. The changes of growth parameters, photosynthetic and non-photosynthetic pigments and potassium content showed that the addition of 1 mM AsA and/or 0.05 mM GA3 considerably decreased the oxidative damage in common bean plants treated with 200 mM NaCl. The NaCl-stressed seedlings exposed to AsA or GA3, specifically in their combination, exhibited an improvement in sodium accumulation in both roots and shoots, as compared to NaCl-treated plants. NaCl treatment increased hydrogen peroxide (H2O2) content and lipid peroxidation indicated by accumulation of malondialdehyde (MDA), whereas the interaction of AsA with GA3 decreased the amounts of MDA and H2O2. In the meantime, interactive effect of these substances enhanced protein content and the activity of the antioxidant enzyme, guaiacol peroxidase, in common bean plants under salt stress. It was concluded that synergistic interaction between AsA and GA3 could alleviate the adverse effects of salinity on P. vulgaris seedlings.