Drought stress mitigation by foliar application of L-carnitine and its effect on radish morphophysiology.

Drought is the major abiotic stress limiting crop production worldwide, with drought events being expected to be harsher and more frequent due to the global warming. In this context, the development of strategies to mitigate the deleterious effects of drought, such as the use of biostimulants, is imperative. Radish is a globally cultivated root vegetable, with high nutritional and phytochemical value. Thus, this study aimed to evaluate the potential of exogenous carnitine application in the mitigation of drought stress on radish morphophysiology. For this, radish plants were grown for 30 days, being irrigated with 80% (well-watered) or 15% (drought stress) of water holding capacity and sprayed with carnitine (5, 50, and 500 µM) or water (0 µM-no carnitine). The experimental design was completely randomized, in a 4 × 2 factorial scheme (carnitine concentrations × water conditions) with six replicates, and each experimental unit consisted of one plant. The gas exchanges, chlorophyll a fluorescence, photosynthetic pigments, electrolyte leakage, relative water content, and biomass production and allocation were evaluated. Drought reduced the photosynthetic capacity of plants by impairing water balance and membrane integrity, decreasing biomass accumulation, mainly in globular roots. The application of low carnitine (5 µM) mitigated these negative effects caused by drought, increasing membrane integrity and water balance of plants, while higher carnitine concentration (50 and 500 µM) aggravated drought stress. This study highlights the potential of carnitine in the mitigation of drought stress on radish plants, supporting its role as a biostimulant. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01308-6.

Salicylic acid mitigates the effects of mild drought stress on radish (Raphanus sativus) growth.

Water deficit is the most critical factor limiting plant growth and production and salicylic acid (SA) has potential for stress mitigation in plants; therefore, we evaluated the effect of SA on radish (Raphanus sativus L.) growth and ecophysiology under water deficit. Plants were sprayed with SA (100µM) or water (control), and irrigated at 80% (W80), 60% (W60), 40% (W40), and 20% (W20) of field capacity. The SA treatments and drought stress started 7days after sowing and lasted until the end of the cycle (30days after sowing). The morphophysiological analyses showed that radish plants had impaired growth at the lower water supply levels, but the treatment with SA reversed these growth restraints under moderate stress, leading to increases in shoot mass at W40 and storage root mass at W60 and W40. SA treatment also reversed the reduction of storage root volume at W60. The tendency of water deficit to increase F O and reduce F V /F M suggests possible damage to the photosystem II of drought-stressed plants. The parameters of gas exchange and photosynthetic pigments showed maintained photosynthetic efficiency, but total photosynthesis decreased due the lower shoot dry mass. Overall, exogenously applied SA reversed the growth restraints at W60 and W40, which revealed that SA was effective in mitigating the effects of moderate water deficit on biomass accumulation and partitioning in radish plants.

Spermine reduces the harmful effects of salt stress in Tropaeolum majus.

Flowers, leaves, fruits and buds of Tropaeolum majus are used for ornamental, medicinal and food purposes. However, salt stress limits the development and productivity of T. majus due to biochemical, physiological and anatomical disturbances. Polyamine application is an alternative for mitigating the harmful effects of salt stress. Thus, the objective of this work was to evaluate the effects of spermine application in T. majus grown under salt stress. The experiment was carried out in a completely randomized design, in a 3 × 2 factorial scheme, with 0, 40 mM (moderate salt stress) and 80 mM (severe salt stress) NaCl, and 0 and 1 mM spermine, and with five replicates. Growth (plant height, stem diameter, number of leaves, number of flowers, number of buds, leaf dry mass, stem dry mass and flower dry mass), gas exchange (gs, A, E, Ci and WUE), relative water content, contents of free amino acids, phenolic compounds, reducing and non-reducing sugars, lipid peroxidation and enzymatic activities (CAT, POD and APX) were evaluated. Spermine application decreased the harmful effects of salt stress on the growth and gas exchange and increased flowering in T. majus. Furthermore, the relative water content of T. majus increased under severe salt stress conditions. Spermine application reduced the contents of total phenolic compounds, free amino acids, reducing sugars and non-reducing sugars on leaves of T. majus. Spermine application increased CAT and POD activities in plants under severe salt stress and POD and APX in plants under moderate salt stress.

Climatic Variation on Gas Exchange and Chlorophyll a Fluorescence in Tabebuia roseoalba and Handroanthus heptaphyllus (Bignoniaceae)

Abstract: Climatic variation throughout the day influences the ecophysiological performance of plants at different growth stages and phases. Therefore, this work aimed to evaluate the effect of climatic variation on ecophysiological aspects of T. roseoalba and H. heptaphyllus at different hours of the day and indicate the ideal time for measuring ecophysiological variables in these species. The research was carried out in a greenhouse at the forest nursery of the Federal University of Paraíba, Campus II, in the municipality of Areia, Paraíba state, Northeastern Brazil. The experimental design was completely randomized, consisting of 10 evaluation times throughout the day (from 8 am to 5 pm), with 1 h hour interval between each evaluation. Temperature and air relative humidity inside and outside the greenhouse were evaluated to understand the effect on gas exchange (net assimilation rate of CO2, stomatal conductance, transpiration rate, internal concentration of CO2, and vapor-pressure deficit) and chlorophyll a fluorescence (initial, maximum, and variable fluorescence, photochemical quenching, and electron transport rate). Data were submitted to canonical correlation analysis and principal component analysis to verify the relationship between climatic and ecophysiological variables. For both species, higher correlation was found between internal and external relative humidity with all the ecophysiological variables analyzed, except for initial fluorescence. Thus, climatic factors influenced the photosynthetic performance of T. roseoalba and H. heptaphyllus plants, and 8 am to 9 am is indicated for carrying out ecophysiological evaluations in both species.

Impact of biostimulant and saline water on cape gooseberry (Physalis peruviana L.) in Brazil.

Production of Physalis peruviana L. has gained prominence in Northeastern Brazil. However, salinity limits the crop development in the Brazilian semiarid. Thus, this research aimed to evaluate the application of Acadian® biostimulant as mitigant of the deleterious effects of salinity on growth and gas exchange of P. peruviana plants. The experiment was combining different electrical conductivity of irrigation water (0.50, 1.23, 3.00, 4.44, and 5.50 dS m-1) and biostimulant doses (0.00, 1.45, 5.00, 8.55, and 10.00 mL L-1). The main variables evaluated were plant height, stem diameter, number of leaves, root length, leaf area, specific leaf area, leaf area ratio, absolute and relative growth rate for plant height, and gas exchange. Experimental results showed that an increase in electrical conductivity of irrigation water had negatively affected the growth components and gas exchange in P. peruviana. Also, the application of seaweed-based biostimulant improves the photosynthetic capacity (43.3%), reduces transpiration rate (26.5%) and water loss by this process, further it attenuated the deleterious effects of salinity on specific leaf area, leaf area ratio, and stomatal conductance. To further elucidate the effectiveness of biostimulant application as a mitigant of salt stress, research aimed at the biochemical and enzyme activities of the plant's antioxidant system should be conducted to better understand this process.

Gas exchanges and chlorophyll content in green pepper plants under bio-fertilization and times of application

This study aimed to determine the gas exchange and the chlorophyll content of green pepper plants under doses and times of application of bio-fertilizers based on manure and enriched organic compost. Two experiments were carried out simultaneously with applications of bio-fertilizers prepared from manure and enriched organic compost, one using cattle manure (CBF) and the other sheep manure (SBF). For these, four doses of biological fertilizers (100, 200, 300 and 400 dm³ ha-1), three application times (0, 30 and 60 days after transplantation - DAT) and absolute control, referring to the absence of fertilization, were used. treatments. were arranged in a randomized block design, totaling 13 treatments. The variables evaluated were: the relative chlorophyll a, b and total content; liquid photosynthesis (A); stomatal conductance (gs); internal CO2 concentration (Ci); instant carboxylation efficiency (iCE - A/Ci); transpiration rate (T); intrinsic water use efficiency (iWUE - A/gs); and water use efficiency (WUE - A/E). Gs, A and T, showed significant effect at 60 DAT with the application of SBF and Ci at 30 DAT with CBF. The dose of 400 dm³ ha-1 of SBF provided greater gas results, and the doses of 200 and 300 dm³ ha-1 of CBF promoted a greater Ci, greater stomatal conductance, greater liquid photosynthesis and better water use efficiency, which results in a greater plant fresh weight at the time of flowering induction.

Photosynthesis of Physalis peruviana under different densities of photons and saline stress

Physalis peruviana L. is a solanacea that has been gaining prominence due to its fruits presenting good acceptance in the national and international market. However, several abiotic factors, such as salinity, can cause physiological disturbances in plants, and these changes may be of greater or lesser intent according to species. Therefore, the objective of the present work was to evaluate the physiological behavior of P. peruviana submitted to different fluxes of photosynthetically active photons (PPFD) and saline stress. The experimental design was a randomized block design with three saline levels (ECw) (0.5, 2.75 and 5.00 dS m-1) with four replications. Gas exchange measurements were performed with a portable infrared gas analyzer. Liquid CO2 assimilation, stomatal conductance, internal CO2 concentration, water use efficiency and instantaneous carboxylation efficiency were measured. Data were subjected to analysis of variance by F test and in cases of significance applied to regression analysis. The increase in PPFD provided reductions in stomatal conductance up to the density of approximately 400 µmol m-2s-1, being more pronounced in ECw of 2.75 and 5.0 dS m-1. The maximum CO2 assimilation rates in the three salinities are different according to the PPFD. The salinity of irrigation water reduced the quantum efficiency of photosynthesis in P. peruviana plants.

Macronutrient uptake, transport and use efficiency in seedlings of Pochota fendleri produced in different substrates / Eficiência de absorção, transporte e utilização de macronutrientes por mudas de Pochota fendleri produzidas em diferentes substratos

Seedlings produced in containers can be influenced by the materials used in the substrate, which affects the robustness of the plants and, indirectly, the time required for transplanting and for the plants to become established in the field. The aim of this study was to determine the chemical properties of different materials and on the absorption of macronutrients in Pochota fendleri seedlings (cedro-doce). The treatments were: sand (Sa), soil (So), sand+soil (Sa+So), and sand+soil+crushed Brazil nut capsules (Sa+So+CNC). The growth and macronutrient content were evaluated at 60 days after thinning. The amount of macronutrients in the substrate increased with the addition of crushed Brazil nut capsules. The use of different materials for the substrate, particularly Sa+So+CNC, had a positive influence on the morphological characteristics of seedlings, which ensuring high rates of establishment and survival after outplanting, making commercial reforestation with Pochota fendleri attractive.

As mudas produzidas em recipientes podem ser influenciadas pelos materiais utilizados no substrato, que afetam a robustez das plantas e, indiretamente, o tempo necessário para o transplante e o estabelecimento das plantas no campo. O objetivo deste estudo foi determinar as propriedades químicas de diferentes materiais e a absorção de macronutrientes em mudas de Pochota fendleri (cedro-doce). Os tratamentos foram: areia (Sa), solo (So), areia + solo (Sa + So) e areia + solo + casca de ouriço da castanha do Brasil triturada (Sa + So + CNC). O crescimento e o teor de macronutrientes foram avaliados 60 dias após o desbaste. A quantidade de macronutrientes no substrato aumentou com a adição de casca de ouriço da castanha do Brasil triturada. O uso de diferentes materiais para o substrato, principalmente o Sa + So + CNC, influenciou positivamente as características morfológicas das mudas, garantindo altas taxas de estabelecimento e sobrevivência após o plantio, tornando atraente o reflorestamento comercial com Pochota fendleri.