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.

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.

Application times and doses of bovine and sheep biofertilizers in the morphophysiological characteristics of green pepper plants

This study aimed to evaluate the morphological characteristics and leaf area of Solário hybrid green pepper plants under different doses and times of application of organic fertilizers based on manure and enriched organic compounds. Two experiments were carried out with applications of organic fertilizers based on manure and enriched organic compounds, using bovine manure (CBF) and sheep manure (SBF). A randomized block experimental design was used was in factorial scheme 4 x 3 + 1, with three replications, composed by the doses of biological fertilizers (100, 200, 300 and 400 dm³ ha-1), application times (0, 30 and 60 days after transplantation - DAT) and control. The following variables were evaluated: plant height (AP); canopy width (LC); stem diameter (DC); leaf number (NF); leaf length (CF); leaf width (LF); and leaf area (PA). The dose of 100 g L-1 of Bovine biofertilizer (CBF) applied at 30 and 60 DAT is indicated for hybrid green peppers cv Solário cultivation since it promoted greater expansion of leaf area. Bovine and sheep fertilizer are indicated to promote plant height, canopy width, stem diameter and number of leaves in hybrid green pepper cv Solário plants.

CRESCIMENTO DO MARACUJAZEIRO AMARELO SOB ESTRESSE SALINO E BIOFERTILIZAÇÃO EM AMBIENTE PROTEGIDO CONTRA PERDAS HÍDRICAS

O objetivo do trabalho foi avaliar a influência do biofertilizante bovino e cobertura morta vegetal no crescimento vegetativo do maracujazeiro amarelo irrigado com água não salina e salina em ambiente protegido contra perdas hídricas. O experimento foi conduzido no período de outubro de 2008 a abril de 2009, no município de Remígio, Paraíba. O delineamento estatístico foi em blocos casualizados, em esquema fatorial 2x2x2, referente à água não salina (0,5 dS m-1) e salina (4,5 dS m-1), sem e com biofertilizante bovino, sem e com cobertura morta, com três repetições e três plantas por parcela. Avaliaram-se o período para poda do broto apical, taxa de crescimento absoluto em altura, comprimento de internódio, número de ramos produtivos e diâmetro do caule das plantas. O aumento do nível de salinidade da água, independentemente da adição do biofertilizante, inibiu o crescimento das plantas. O período do transplantio à poda do broto apical das plantas irrigadas com água salina e o uso do biofertilizante foi antecipado em 8,16 dias. O maior crescimento em altura do maracujazeiro amarelo ocorreu no solo com biofertilizante e cobertura morta.