Summer Plants Research Articles

Winter cover cropping increases albedo and latent heat flux in a Texas High Plains agroecosystem

AbstractWinter cover crops represent a land cover change that may sequester carbon in the soil and improve agricultural sustainability. Their adoption may also change the Earth's radiative balance and result in biophysical feedbacks to climate through alterations in albedo and latent heat fluxes. Understanding the mechanisms underlying these alterations to the radiative balance is important for making reliable future climate projections. However, data on cover crop biophysics are limited, requiring models to rely on data from summer plants for parameterization, likely biasing predictions. To address this gap, we measured the albedo and stomatal conductance of two summer crops and three winter crops on farms in the High Plains region of Texas. We also established a winter cover crop field experiment with two cover crops and fallow fields to estimate the change in albedo and latent heat flux that results from a switch to winter cover cropping. We found that albedo was significantly higher in winter‐like conditions than in summer‐like conditions due to an increase in plant albedo and a reduction in leaf area index. The albedo of winter cover crops was higher than the soil albedo, resulting in an increase in top‐of‐atmosphere reflected radiation of 7%–14% when converting from fallow fields to winter cover cropped fields. There was an additional cooling effect through doubling of the estimated latent heat flux caused by the presence of cover crops. The combined changes in albedo and latent heat resulted in a change in the surface energy balance that is associated with an overall cooling effect of winter cover crops on surface atmospheric temperatures. While this effect is likely to be region‐specific, these results strongly indicate that winter cover crops alter the surface albedo and latent heat flux of agricultural fields and provide a direct cooling effect in the High Plains region of Texas.

Dynamic Reconfiguration of Switchgrass Proteomes in Response to Rust (Puccinia novopanici) Infection.

Switchgrass (Panicum virgatum L.) can be infected by the rust pathogen (Puccinia novopanici) and results in lowering biomass yields and quality. Label-free quantitative proteomics was conducted on leaf extracts harvested from non-infected and infected plants from a susceptible cultivar (Summer) at 7, 11, and 18 days after inoculation (DAI) to follow the progression of disease and evaluate any plant compensatory mechanisms to infection. Some pustules were evident at 7 DAI, and their numbers increased with time. However, fungal DNA loads did not appreciably change over the course of this experiment in the infected plants. In total, 3830 proteins were identified at 1% false discovery rate, with 3632 mapped to the switchgrass proteome and 198 proteins mapped to different Puccinia proteomes. Across all comparisons, 1825 differentially accumulated switchgrass proteins were identified and subjected to a STRING analysis using Arabidopsis (A. thaliana L.) orthologs to deduce switchgrass cellular pathways impacted by rust infection. Proteins associated with plastid functions and primary metabolism were diminished in infected Summer plants at all harvest dates, whereas proteins associated with immunity, chaperone functions, and phenylpropanoid biosynthesis were significantly enriched. At 18 DAI, 1105 and 151 proteins were significantly enriched or diminished, respectively. Many of the enriched proteins were associated with mitigation of cellular stress and defense.

Características agronômicas e qualidade de cultivares de alface em épocas de cultivo no oeste alagoano

ABSTRACT Growing lettuce under high temperatures and light incidence, as in the Alagoas State hinterland, Brazil, induces early tasseling and decreases the quality of the product. Thus, the objective of this work was to evaluate the production and post-harvest quality of lettuce cultivars in different crop seasons in western Alagoas, Brazil. A randomized block experimental design was used, with four replications. The treatments consisted of lettuce cultivars: Baba-de-Verão, Cinderela, Elba, Mônica, Solaris, and Veneranda. The winter crop was more favorable for plant diameter, except for Baba-de-Verão, whose performance was similar in both seasons and stood out in the summer. The winter crop resulted in better performance in plant height, stem diameter, and fresh matter yield, whereas summer plants reached larger number of leaves. The cultivar Mônica presented longer stem length, denoting lower tolerance to early tasseling and, therefore, it is not indicated to be grown in the region. The cultivar Baba-de-Verão (Lisa group) reached higher fresh matter yield, number of leaves per plant, and stem diameter, and it was the most adequate cultivar to be grown in western Alagoas. Elba, Solaris, and Veneranda were the lettuce cultivars from the Crespa group that stood out. Baba-de-Verão was the cultivar that presented the best performance for chlorophyll a, b, and total. The cultivar Solaris presented the highest carotenoid contents. Plants grown in the winter reached higher chlorophyll a and total, carotenoid contents, pH, and soluble solid (SS) to titratable acidity (TA) ratio, whereas the lettuce grown in the summer had higher SS and TA.

К биологии некоторых представителей душицы обыкновенной Origanum vulgare L. в кул ьтуре

This article presents the results of the study of two growing seasons (2022–2023) of Origanum vulgare L. (common origanum), O. vulgare ssp. virens (Hoffmanns & Link) letsw., O. vulgare “Severnoe Siyanie”, O. vulgare f. aureum. The characteristics of the onset of phenological phases, biomorphological indicators, the yield of green mass of a plant during the flowering phase were studied, the success in the conditions of cultivation in the northern forest steppe of the Bashkir Urals (Ufa) was evaluated. Studies on the biological characteristics of the above mentioned taxa of oreganum were carried out in the South Urals Botanical Garden-Institute of UFRC RAS at the collection site “Aromatic Garden”. Oreganums are perennial, rhizomatous, long-lived, summergreen plants with winter dormancy. According to the flowering period, they belong to the group of average summer plants with a flowering period of one month (a group of long-flowering plants). It was found that under the conditions of cultivation in the Bashkir Urals, the studied oreganum plants undergo a full cycle of life development, including flowering and seed formation (except for O. vulgare f. aureum). All studied forms of common oreganum grow well, develop well, form a well-developed above-ground mass. When evaluating the success of the introduction, the oreganum plants proved to be very resistant to the local climate, which makes it possible to recommend them for widespread use in the creation of herb gardens in the Bashkir Urals.

Summer poisoning hazards to pets

As the spring turns to summer, owners and their pets will spend even more time out of doors. Some venomous animals are more active in the warmer months and there is risk of adder bites or stings from bees, wasps and hornets. Adder bites can result in significant morbidity but low mortality. Insect stings commonly cause local reactions and although these are generally mild, stings involving the airway are more hazardous since there is risk of respiratory obstruction. In addition, there is also a risk of anaphylaxis in sensitive individuals (just as in people) and multiple stings can cause multiorgan damage. Slug and snail killer products are more commonly used in the summer and are therefore more accessible to pets. These commonly contain ferric phosphate rather than metaldehyde which has been banned in the UK, and are less hazardous. Harmful summer plants include those containing cardiac glycosides such as foxglove and oleander. Some plants such as hogweed contain compounds that cause skin damage following dermal contact in combination with exposure to sunlight, and are therefore a particular risk on sunny days.

Heavy metals concentration, and antioxidant activity of the essential oil of the wild mint (Mentha longifolia L.) in the Egyptian watercourses

In the present study, we assessed seasonal variation in the accumulation potential of wild mint (Mentha longifolia) to heavy metals as well as the chemical composition and antioxidant activity of the essential oil of mint in polluted and unpolluted watercourses. The results indicated that the wild mint showed seasonal fluctuations in accumulation potential for heavy metals proved by bioaccumulation factor (BF) and translocation factor (TF). The all measured heavy metals, except Pb were retained in the underground parts. Summer plants accumulated the highest concentrations of Al, Cd, Cr and Fe in their root, while the lowest concentration of Ni in their shoot. The bioaccumulation factor for Cd, Cu, Mn, Ni, Zn and Co was greater than one, while the translocation factor of the investigated metals (except Pb) did not exceed one, indicating the potential of wild mint for phytostabilization of these metals in contaminated wetlands. The yield and composition of mint essential oil (MEO) were affected by harvesting season and heavy metals pollution. GC/MS showed that isomenthone, cis-piperitenone oxide, menthone and pulegone, were the main oil constituents. Mint essential oil show promising antioxidant activity by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay under pollution stress. The maximum reducing power of MEO were obtained during autumn and summer seasons (polluted canals).In conclusion, summer is the ideal season for harvesting wild mint plants for the maximum plant biomass, oil yield, high radical scavenging activity of MEO and to monitor pollution in contaminated wetlands.

The Residual Allelopathic Effects of two Brassicaceae Seed Powder on the Following Summer Plants and Associated Weeds

The Residual Allelopathic Effects of two Brassicaceae Seed Powder on the Following Summer Plants and Associated Weeds

Fall armyworm (Spodoptera frugiperda Smith) feeding elicits differential defense responses in upland and lowland switchgrass.

Switchgrass (Panicum virgatum L.) is a low input, high biomass perennial grass being developed for the bioenergy sector. Upland and lowland cultivars can differ in their responses to insect herbivory. Fall armyworm [FAW; Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae)] is a generalist pest of many plant species and can feed on switchgrass as well. Here, in two different trials, FAW larval mass were significantly reduced when fed on lowland cultivar Kanlow relative to larvae fed on upland cultivar Summer plants after 10 days. Hormone content of plants indicated elevated levels of the plant defense hormone jasmonic acid (JA) and its bioactive conjugate JA-Ile although significant differences were not observed. Conversely, the precursor to JA, 12-oxo-phytodienoic acid (OPDA) levels were significantly different between FAW fed Summer and Kanlow plants raising the possibility of differential signaling by OPDA in the two cultivars. Global transcriptome analysis revealed a stronger response in Kanlow plant relative to Summer plants. Among these changes were a preferential upregulation of several branches of terpenoid and phenylpropanoid biosynthesis in Kanlow plants suggesting that enhanced biosynthesis or accumulation of antifeedants could have negatively impacted FAW larval mass gain on Kanlow plants relative to Summer plants. A comparison of the switchgrass-FAW RNA-Seq dataset to those from maize-FAW and switchgrass-aphid interactions revealed that key components of plant responses to herbivory, including induction of JA biosynthesis, key transcription factors and JA-inducible genes were apparently conserved in switchgrass and maize. In addition, these data affirm earlier studies with FAW and aphids that the cultivar Kanlow can provide useful genetics for the breeding of switchgrass germplasm with improved insect resistance.

A Comparative Study of Essential Oil Constituents and Phenolic Compounds of Arabian Lilac (Vitex Trifolia var. Purpurea): An Evidence of Season Effects.

To evaluate the fluctuation of secondary metabolites in Arabian lilac during a year, aerial parts of the plant were harvested in the middle of each month. The essential oils content from fresh and dried plant materials was analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometer (GC-MS), individually. Phytochemical contents, along with antiradical scavenging potential of the related methanol extracts were separately assessed. The spring and autumn samples (fresh and dried) yielded more essential oil than the other samples. Forty-one compounds were identified totally in the oils and the major constituents characterized were β-caryophyllene, sabinene, and caryophyllene oxide. The extracts obtained from winter and summer plants possessed the highest total phenolics. The maximum amount of total flavonoid content was measured in winter (December and January), whereas the minimum one was observed in spring (March). The summer and winter samples showed the highest and lowest content of flavones and flavanols, respectively, whereas the anthocyanin content was higher in winter than in summer. Moreover, antiradical activity of the extracts in summer and winter samples was higher than in other seasons. Overall, this study can provide useful information regarding the best harvest period of Arabian lilac to yield the desired compounds for application in phytopharmaceutical and food industries.

Effect of different methyl jasmonate concentrations on pumpkin (Cucurbita pepo L.) seedling tolerance to chilling stress

اگرچه کشت زودهنگام محصولات بهاره برای استفاده از شرایط معتدل بهاری و همچنین رشد رویشی مناسب اهمیت زیادی دارد ولی وجود دماهای پایین در ابتدای دوره رشد ممکن است رشد گیاه را با تنش سرما مواجه نماید. این آزمایش به‌صورت فاکتوریل شامل شش غلظت متیل جاسمونات (صفر، 1، 5، 50، 100 و 150 میکرومولار) و سه سطح دما (8، 11 و 14 درجه سانتی­گراد) در قالب طرح کاملا تصادفی در شرایط کنترل‌شده در دانشگاه شهرکرد در سال 1395 اجرا شد. در روز یازدهم صفات مورفولوژیکی و بیوشیمیایی اندازه‎گیری شد. نتایج نشان داد که بیشترین طول ریشه‎چه در غلظت 50 میکرومولار متیل جاسمونات و دمای 11 درجه سانتی­گراد با 55.6 درصد افزایش نسبت به شاهد حاصل شد. در دمای 8، 11 و 14 درجه سانتی‌گراد بذرهایی که با متیل جاسمونات تیمار نشده بودند فاقد ساقه‎چه بودند. در دمای هشت درجه سانتی­گراد، غلظت پنج میکرو مولار بیشترین طول ریشه ­چه، طول ساقه­ چه و وزن خشک ساقه­ چه را داشت. در بین تیمارهای متیل جاسمونات، بیشترین میزان فعالیت آنزیم‎های گایاکول پراکسیداز و کاتالاز نیز در غلظت پنج میکرومولار مشاهده شد. در دمای 11 درجه سانتی­گراد، غلظت پنج میکرومولار به علت افزایش طول ساقه­ چه، وزن خشک ریشه­ چه، میزان فعالیت آنزیم کاتالاز نسبت به سایر غلظت‎ها برتری داشت و ازلحاظ طول ریشه ­چه و فعالیت آنزیم سوپر اکسید دیسموتاز در رتبه دوم قرار گرفت. در دمای 14 درجه سانتی­گراد، غلظت 50 میکرومولار دارای بیشترین وزن خشک ریشه­ چه، وزن خشک ساقه­ چه و میزان فعالیت آنزیم­ های سوپراکسیددیسموتاز، گایاکول پراکسیداز و کاتالاز بود. در دمای 14 درجه سانتی­گراد، بیشترین میزان طول ساقه ­چه و شاخص بنیه بذر در پنج میکرومولار مشاهده شد و از این لحاظ غلظت 50 میکرومولار در رتبه دوم قرار گرفت. به‌طورکلی نتیجه‎گیری می‎شود که کاربرد متیل جاسمونات باعث افزایش فعالیت آنزیم‎های آنتی‌اکسیدان و درنتیجه تحمل گیاهچه کدوی پوست‌کاغذی به تنش دمای پایین می­شود.

야쿠티아의 동토지역에 서식하는 생물의 추운기후-순화의 조절에서 식물 지방산의 역할

Vegetative plants in Yakutia are naturally frozen when they are covered with snow in the fall, and they function as green cryo-fodder that is a source of biologically active substances and nutrients for herbivorous animals. We observed a considerable increase in the total fatty acid content in the leaves of Avena sativa, Elytrigia rеpens, Equisetum variegatum and Equisetum scirpoides during the fall period. However, the degree of unsaturation of fatty acids was not higher in the frozen plants covered with snow than in the summer plants, with the exception of E. scirpoides, a dwarf horsetail found in the Pole of Cold in the northern hemisphere. In the internal adipose tissue of the Yakut horse (young horse meat), 18 fatty acids were found, including 10 saturated ones. Monounsaturated oleic С18:1 (n-9) acid and polyunsaturated α-linolenic С18:3 (n-3) acid were equally prevalent among the unsaturated fatty acids, accounting for 70% of the total unsaturated fatty acids. This composition of polyenoic fatty acids in the internal adipose tissue indicates that the Yakut horse actively feeds on the fall vegetation and the wintergreen sedge-grass. We believe that the high plant-specific free fatty acid content in the tissue of Yakut horses may play an important role in the regulation of their resistance to long-term low-temperature stress.

Traits of seasonal dimorphism associated with adaptation to cold stress in Origanum dictamnus L. (Lamiaceae)

Phryganic plants are herbs or subshrubs with erect shoots that grow at low altitudes under hot and arid environmental conditions. Many phryganic plants are aromatic/medicinal plants and display the phenomenon of seasonal dimorphism (Thymus sibthorpii, Satureja thymbra, Cistus incanus, Phlomis fruticosa, Teucrium polium, etc.). Phryganic plants of the Mediterranean region are reported so far to be affected by summer drought stress. However, in the present study, the phryganic plant Origanum dictamnus appears to be affected by winter cold stress rather than by summer drought stress in the specific area. This triggered the investigation of the functional and structural traits associated with adaptation of O. dictamnus to cold stress. Winter plants of O. dictamnus in order to stand up to the cold, shed all of their large leaves and keep only the small apical leaves, which are covered with a thick insulating layer of dendroid non-glandular hairs. Epidermal and mesophyll cells of apical leaves contain antioxidant vacuolar phenolics protecting from oxidative stress due to low temperatures. Protection from oxidative stress is also provided by the antioxidant essential oils secreted by the numerous glandular hairs. Concentrations of stress indicators like proline and soluble sugars, are always higher in winter leaves compared to summer leaves. Principal components of the O. dictamnus essential oil are p-Cymene, Carvacrol, γ-Terpinene, and Borneol. The major constituent of the winter oil is p-Cymene (59.2%) and that of the summer oil Carvacrol (42.4%). The presented results provide a structural and functional elucidation for the largely deviating appearance of winter and summer plants of O. dictamnus, and favour the interpretation of adaptation of the plant to cold stress.

Contrasting metabolism in perenniating structures of upland and lowland switchgrass plants late in the growing season.

BackgroundSwitchgrass (Panicum virgatum L.) is being developed as a bioenergy crop for many temperate regions of the world. One way to increase biomass yields is to move southern adapted lowland cultivars to more northern latitudes. However, many southerly adapted switchgrass germplasm can suffer significant winter kill in northerly climes.Materials and MethodsHere, we have applied next-generation sequencing in combination with biochemical analyses to query the metabolism of crowns and rhizomes obtained from two contrasting switchgrass cultivars. Crowns and rhizomes from field-grown lowland (cv Kanlow) and upland (cv Summer) switchgrass cultivars were collected from three randomly selected post-flowering plants. Summer plants were senescing, whereas Kanlow plants were not at this harvest date.ResultsPrincipal component analysis (PCA) differentiated between both the Summer and Kanlow transcriptomes and metabolomes. Significant differences in transcript abundances were detected for 8,050 genes, including transcription factors such as WRKYs and those associated with phenylpropanoid biosynthesis. Gene-set enrichment analyses showed that a number of pathways were differentially up-regulated in the two populations. For both populations, protein levels and enzyme activities agreed well with transcript abundances for genes involved in the phenylpropanoid pathway that were up-regulated in Kanlow crowns and rhizomes. The combination of these datasets suggests that dormancy-related mechanisms had been triggered in the crowns and rhizomes of the Summer plants, whereas the crowns and rhizomes of Kanlow plants had yet to enter dormancy.ConclusionsDelayed establishment of dormancy at more northerly latitudes could be one factor that reduces winter-survival in the high-yielding Kanlow plants. Understanding the cellular signatures that accompany the transition to dormancy can be used in the future to select plants with improved winter hardiness.

Characterization of Greenbug Feeding Behavior and Aphid (Hemiptera: Aphididae) Host Preference in Relation to Resistant and Susceptible Tetraploid Switchgrass Populations

Two choice studies were performed to evaluate greenbug, Schizaphis graminum (Rondani), and yellow sugarcane aphid, Sipha flava (Forbes), preference for two tetraploid switchgrass populations, Summer and Kanlow, and one experimental hybrid, K × S, derived by crossing Kanlow (male) × Summer (female) plants. Additionally, an assessment of S. graminum feeding behavior was performed on the same switchgrass populations, by using the electrical penetration graph (EPG) technique. Choice studies for S. flava indicated a lack of antixenosis, with no preference by aphids among any of the switchgrass populations at any time point. However, choice studies with S. graminum indicated a preference for the K × S plants at 24 h after aphid introduction. No obvious differences were observed for the leaf surfaces between the three populations. Feeding behavior studies for S. graminum on switchgrasses indicated no differences for the time to first probe or time to first sieve element phase among switchgrass populations. However, duration of sieve element phases for S. graminum was significantly less on Kanlow compared to K × S and Summer. S. graminum also had a significantly lower potential phloem ingestion index (PPII) and few aphids showing sustained phloem ingestion on Kanlow as compared to K × S and Summer plants. These results suggest that resistance factors (chemical or mechanical) in Kanlow are located in the phloem tissue. At the whole leaf level, some differences were observed for a subset of polar metabolites, although Kanlow plants were significantly enriched for oxalic acid.

Categories of Resistance to Greenbug and Yellow Sugarcane Aphid (Hemiptera: Aphididae) in Three Tetraploid Switchgrass Populations

Switchgrass, Panicum virgatum L., has been targeted as a bioenergy feedstock. However, little is currently known of the mechanisms of insect resistance in this species. Here, two no-choice studies were performed to determine the categories (antibiosis and tolerance) and relative levels of resistance of three switchgrass populations (Kanlow–lowland ecotype, Summer–upland ecotype, and third generation derivatives between Kanlow × Summer plants, K×S) previously identified with differential levels of resistance to the greenbug, Schizaphis graminum (Rondani), and yellow sugarcane aphid, Sipha flava (Forbes). No-choice studies indicated that Kanlow possessed multi-species resistance, with high levels of antibiosis to both aphid species, based on aphid survival at 7 and 14 days after aphid introduction and cumulative aphid days, while K×S possessed low-to-moderate levels of antibiosis to S. flava. Further, functional plant loss indices based on plant height and biomass indicated that tolerance is an important category of resistance for Summer plants to S. graminum. These studies also indicated that Summer lacks both tolerance and antibiosis to S. flava, relative to the other switchgrasses tested, whereas K×S lack tolerance and antibiosis to S. graminum. These studies are the first attempt to analyze the categories of resistance in switchgrass and provide critical information for characterizing the biological mechanisms of resistance and improving our knowledge of the plant–insect interactions within this system.

Glandular and non-glandular hairs in the seasonally dimorphic Origanum dictamnus L. (Lamiaceae) as a means of adaptation to cold stress

<em>Origanum dictamnus</em> is a seasonally dimorphic plant having different appearance in winter and summer. Shoots of winter plants are leaf-naked except for their apical region which bears a cluster of small leaves covered with a thick indumentum of non-glandular hairs. This indumentum highly contributes to the avoidance of cold penetration into the leaf mesophyll, allowing thus plants to endure winter low temperatures. Shoots of summer plants are vigorous with large green leaves. Non-glandular hairs are dendroid with a 5-celled vertical stub and several lateral branches. Glandular hairs are of two types, large peltate hairs and small capitate hairs. Peltate hairs are numerous and consist of a 12-celled head, a unicellular stalk, and a basal epidermal cell.. They constitute the sites of essential oil secretion. Capitate hairs occur in a small number and are composed of a unicellular head, a unicellular stalk and a basal epidermal cell. They are not secreting essential oil, but a hydrophilic material. The oil secreted by the peltate hairs has antioxidant properties, opposes the oxidative stress resulted from low temperatures, and contributes to the adaptation of the plant to winter cold stress.

Seasonal changes in phenolic compounds and in the biological activities of Baccharis dentata (Vell.) G.M. Barroso

Baccharis, a large genus of Asteraceae, has been extensively studied because of the medicinal properties of its species. The present study determined the seasonal variation of the levels of total phenolic compounds and flavonoids of Baccharis dentata, and determined the antioxidant and bactericidal potential of the plant extracts. Aerial parts of B. dentata were harvested during the seasons of 1 year. Samples of 0.1g dry mass (DM) were extracted with aqueous methanol (80%; v/v), and used for quantification of phenolic compounds, quercetin-derived flavonoids and antioxidant activity (DPPH). Caffeic acid and the flavonoids rutin, quercetin, apigenin and kaempferol were quantified in methanolic extracts (0.5g DM) by HPLC. The micro-dilution method was applied for the determination of the minimal inhibitory concentration (MIC) of selected bacteria strains. Concentrations of total phenolic compounds and flavonoids showed significant seasonal variation, and the antioxidant potential of extracts was related to the concentration of these compounds. Highest antioxidant activity was detected in the extracts from summer and winter plants. Concentrations of quercetin, kaempferol and apigenin were markedly higher in spring and summer plants when compared to the other seasons. This result may be related to the antibacterial activity of n-butanolic and aqueous fractions against Staphylococcus aureus. This is the first report on seasonal changes of secondary compounds and biological activities on B. dentata and might be useful to prospection of novel molecules with antioxidant and antimicrobial properties.

Cabbage Seasonal Leaf Quality Mediating the Diamondback Moth Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) Performance.

Seasonal variation in plant quality may be intense enough to generate predictable patterns in insect herbivore populations. In order to explain seasonal oscillations in neotropical populations of the diamondback moth Plutella xylostella (L.), we tested the following: (1) if nutritional quality of cabbage (Brassica oleraceae var. capitata), a primary host plant of diamondback moth, adversely affects the performance of this insect in late spring and early summer, when populations decline and go extinct, and (2) if nutritional features of cabbage change with the seasons. We measured the performance of diamondback moth reared on leaves of cabbages grown during the four seasons of the year. Summer plants proved to be worse for the survival of the immature stages and subsequent adult fecundity, but there were no significant differences between the remaining seasons. Our results support the hypothesis that short-lived plants, grown in different seasons of the year in the tropics, have different nutritional and defensive attributes. We analyzed nutritional quality of cabbage leaves from the four seasons, but only total lipids were reduced in summer plants. Neotropical populations of diamondback moth collapse before plant quality decay in the summer. If the diamondback moth is well adapted to the seasonal deterioration of the habitat, including the reduction in the quality of host plants, it is expected that emigration happens before the mortality increases and natality decreases during the summer.

Seasonal variation in agar composition and properties from Gracilaria gracilis (Gracilariales, Rhodophyta) of the Patagonian coast of Argentina

SummarySeasonal variation of agar from specimens of a commercially exploited population of Gracilaria gracilis (Stackhouse) Steentoft, Irvine & Farnham in the Patagonian coast of Argentina was studied. For each seasonal harvest, random samples of plants were pooled for subsequent polysaccharide extraction at different water temperatures and agar physico‐chemical properties and composition were determined.Both spring and summer plants yielded 30% and 41% of agar, respectively, which differed slightly in their at rest rheological behavior. Spring and summer plants produced strong gels (238 and 218 g cm−2, respectively), but the latter gels had nil adhesiveness. In autumn plants, agar yield decayed to 19%, though the product still maintained similar gel strength (210 g cm−2). Adhesiveness in this product was at least an order of magnitude higher than in the others, concomitant with a peak in the formation of tetraspores and carpospores. This suggests a biological role for the galactan in the initial attachment of spores to the substrate. But since fall corresponds to the settling of reproductive structures, caution should be taken to harvest the algae once spores have been shed from mother plants.

Changes in phenolic composition and antioxidant activities of the edible halophyte Crithmum maritimum L. with physiological stage and extraction method

Most antioxidant phytochemicals isolated from higher plants are polyphenols exhibiting different biological activities. Previous studies have shown that plant phenolic contents and antioxidant activities depend on several factors, mainly environmental conditions, and post-harvesting procedures. The present study aims to assess the influence of these interfering factors on phenolic composition and antioxidant activities (DPPH test, reducing power) of Crithmum maritimum L., a promising food halophyte which attracts an increasing interest in recent years. Results showed that the summer plants (reproductive stage) were richer on phenolic compounds than spring ones (vegetative stage), and consequently exhibited higher antioxidant activities. The comparison of two extraction methods showed that maceration extracts contained greatest amounts of phenolic compounds, while soxhlet ones exhibited higher antiradical and reducing power capacities. Besides, the analysis of variance disclosed that the effect of extraction method (E) was the predominant contributor to these antioxidant properties than the physiological development stage (D) and their interaction (E × D). Chromatographic characterization of C. maritimum phenolic composition using the RP-HPLC revealed the presence of phenolic acids and flavonoids with epigallocatechin as major component. Almost all of the identified compounds were described in the literature as interesting bioactive natural substances that may be used in several fields, such as nutraceuticals, cosmetics and agro-food industry.