Effects of irrigation water salinity and salicylic acid on germination and vigor of Mesosphaerum suaveolens (L. ) Kuntze / Efeitos da salinidade da água de irrigação e do ácido salicílico na germinação e no vigor de Mesosphaerum suaveolens (L. ) Kuntze

Salinity is one of the factors that negatively impact plant growth and productivity; therefore, it is necessary to seek solutions that help mitigate the degenerative action of saline stress on crops. The objective of this study was to evaluate the effects of salicylic acid (SA) on the germination and vigor of Mesosphaerum suaveolens (L.) Kuntze seeds subjected to salinity. The experiment was carried out using a completely randomized design, in an incomplete 5 × 5 factorial scheme, with five levels of electrical conductivity of irrigation water (ECw - 0.0, 1.45, 5.00, 8.55, and 10.00 dS m-1) and five doses of SA (0.0, 0.29, 1.00, 1.71, and 2.00 mM), with four replications of 50 seeds, totaling nine combinations generated via a central composite design. The germination percentage, first germination count, germination speed index, average germination time, percentage of abnormal seedlings, shoot, root, and seedling lengths, and total seedling dry mass were evaluated. Salicylic acid attenuated the effect of saline stress on initial growth, mitigating damage to root and shoot lengths. Seed priming with salicylic acid improved germination and seed vigor.(AU)

A salinidade é um dos fatores que promove a inibição no crescimento e produtividade vegetal, sendo necessária a busca por alternativas que auxiliem na mitigação da ação degenerativa do estresse salino às culturas. Objetivou-se com este trabalho avaliar doses de ácido salicílico na germinação e vigor de sementes de Mesosphaerum suaveolens (L.) Kuntze submetidas à salinidade. O experimento foi conduzido em delineamento inteiramente casualizado, em esquema fatorial incompleto 5 x 5, com cinco níveis de condutividade elétrica da água de irrigação (CEa de 0,0; 1,45; 5,00; 8,55 e 10,00 dS m-1) e cinco doses de AS de (0,0; 0,29; 1,00; 1,71 e 2,00 mM L-1), com quatro repetições de 50 sementes, totalizando nove combinações geradas via matriz Composto Central de Box. As variáveis avaliadas foram: porcentagem de germinação, primeira contagem de germinação, índice de velocidade de germinação, tempo médio de germinação, porcentagem de plântulas anormais, comprimento da parte aérea, radícula e plântula e massa seca total de plântulas. O ácido salicílico atenua o efeito do estresse salino sobre o crescimento inicial, mitigando os danos sobre o comprimento de radícula e da parte aérea. O tratamento das sementes com ácido salicílico melhora a germinação e o vigor das sementes.(AU)

How climate change might influence the potential distribution of weed, bushmint (Hyptis suaveolens)?

Invasive species and climate change are considered as the most serious global environmental threats. In this study, we investigated the influence of projected global climate change on the potential distribution of one of the world's most successful invader weed, bushmint (Hyptis suaveolens (L.) Poit.). We used spatial data on 20 environmental variables at a grid resolution of 5 km, and 564 presence records of bushmint from its native and introduced range. The climatic profiles of the native and invaded sites were analyzed in a multi-variate space in order to examine the differences in the position of climatic niches. Maximum Entropy (MaxEnt) model was used to predict the potential distribution of bushmint using presence records from entire range (invaded and native) along with 14 eco-physiologically relevant predictor variables. Subsequently, the trained MaxEnt model was fed with Hadley Centre Coupled Model (HadCM3) climate projections to predict potential distribution of bushmint by the year 2050 under A2a and B2a emission scenarios. MaxEnt predictions were very accurate with an Area Under Curve (AUC) value of 0.95. The results of Principal Component Analysis (PCA) indicated that climatic niche of bushmint on the invaded sites is not entirely similar to its climatic niche in the native range. A vast area spread between 34 ° 02' north and 28 ° 18' south latitudes in tropics was predicted climatically suitable for bushmint. West and middle Africa, tropical southeast Asia, and northern Australia were predicted at high invasion risk. Study indicates enlargement, retreat, or shift across bushmint's invasion range under the influence of climate change. Globally, bushmint's potential distribution might shrink in future with more shrinkage for A2a scenario than B2a. The study outcome has immense potential for undertaking effective preventive/control measures and long-term management strategies for regions/countries, which are at higher risk of bushmint's invasion.

Suaveolic acid: a potent phytotoxic substance of Hyptis suaveolens.

Hyptis suaveolens (Lamiaceae) is an exotic invasive plant in many countries. Earlier studies reported that the aqueous, methanol, and aqueous methanol extract of H. suaveolens and its residues have phytotoxic properties. However, to date, the phytotoxic substances of this plant have not been reported. Therefore, the objectives of this study were isolation and identification of phytotoxic substances of H. suaveolens. Aqueous methanol extract of this plant was purified by several chromatographic runs through bioassay guided fractionation using garden cress (Lepidium sativum) as a test plant. Final purification of a phytotoxic substance was achieved by reverse phase HPLC and characterized as 14α-hydroxy-13ß-abiet-8-en-18-oic acid (suaveolic acid) by high-resolution ESI-MS, (1)H-,(13)C-NMR, CD, and specific rotation. Suaveolic acid inhibited the shoot growth of garden cress, lettuce (Lactuca sativa), Italian ryegrass (Lolium multiflorum), and barnyard grass (Echinochloa crus-galli) at concentrations greater than 30 µM. Root growth of all but lettuce was also inhibited at concentrations greater than 30 µM. The inhibitory activities were concentration dependent. Concentrations required for 50% growth inhibition of suaveolic acid for those test plant species were ranged from 76 to 1155 µM. Therefore, suaveolic acid is phytotoxic and may be responsible for the phytotoxicity of H. suaveolens plant extracts.

Teor e composição química do óleo essencial de Hyptis marrubioides Epling (Lamiaceae) em diferentes genótipos / Essential oil content and chemical composition in Hyptis marrubioides Epl. of different genotypes

Hyptis marrubioides Epling (hortelã-do-campo) é espécie de uso medicinal conhecida pelas suas atividades contra infecções gastrointestinais, infecções de pele, dores e câimbras. Objetivou-se com este trabalho, avaliar o teor e composição química do óleo essencial de H. marrubioides em diferentes genótipos (roxo e branco) e partes da planta fresca (folhas, inflorescências e caule). Os genótipos estudados foram identificados através das inflorescências das plantas que apresentam coloração roxa e branca. O delineamento experimental foi inteiramente casualizado, contendo as três partes da planta de ambos os genótipos, perfazendo um fatorial 3x2, com quatro repetições. O óleo essencial foi extraído por hidrodestilação por duas horas e analisado por Cromatografia Gasosa acoplada a Espectrometria de Massas (CG-EM). O maior teor de óleo essencial foi observado na inflorescência do genótipo roxo. A composição do óleo essencial de H. marrubioides variou quantitativamente entre as partes das plantas analisadas e entre os genótipos. O composto α-tujona apresentou a maior porcentagem de área do pico nas inflorescências de genótipo roxo. As porcentagens das plantas com genótipo roxo foram em média superiores às plantas com genótipo branco.

Hyptis marrubioides Epling ("hortelã-do-campo") is a medicinal species known for its activities against gastrointestinal and skin infections, pains and cramps. The aim of this work was to evaluate essential oil content and chemical composition in H. marrubioides of different genotypes (purple and white), as well as fresh plant parts (leaves, inflorescences and stem). The studied genotypes were identified based on the inflorescences, which are purple and white. The experimental design was completely randomized, including the three parts of both genotypes, in a 3X2 factorial arrangement, with four replicates. Essential oil was extracted through hydrodistillation for two hours and analyzed using Gas Chromatography attached to a Mass Spectrometry (GC-MS). The highest essential oil content was found for the inflorescence of purple genotype. Hyptis marrubioides essential oil composition quantitatively varied among the analyzed plant parts and between genotypes. The compound α-thujone had the highest percentage of apex area in inflorescences of purple genotype. The percentages of purple genotype were on average higher than those of white one.