Photomodulation of strigolactone biosynthesis and accumulation during sunflower seedling growth

Organic foliar spraying: A method that synchronously reduces mercury methylation in soil and accumulation in vegetable

Although the use of foliar spraying with organic matter has been extensively studied and applied to reduce heavy metals in plants, research on its application for reducing mercury (Hg) accumulation in plants, particularly the more toxic methylmercury (MeHg), remains scarce. Furthermore, previous researches on the barrier mechanisms of foliar spraying primarily concentrated on the effects of spraying agents on plant physiological and biochemical indicators, with limited focus on their impacts on soil environment. Herein, the dynamic effects and mechanisms of organic foliar spraying materials, including earthworm liquid fertilizer (ELF), Tween 80 (T80), and citric acid (CA), on soil Hg methylation and accumulation in lettuce were investigated using pot experiment. The findings revealed that foliar spraying significantly reduced the total mercury (THg) and MeHg concentrations in mature lettuce stems and leaves, with CA demonstrating the highest efficacy, achieving reduction rates of 24-60% for THg and 64-69% for MeHg. Spraying CA and T80 also simultaneously reduced the dissolved Hg and MeHg in the soil during the lettuce maturity period. The reductions of soil Hg methylation and bioaccumulation in lettuce were related to the increased abundance of Hg-reducing bacteria, decreased tartaric acid content and Hg-methylating bacteria abundance in soils, as well as enhanced nutrient absorption by lettuce. Additionally, foliar spraying lessened Hg toxicity to the plant and facilitated Hg sequestration in cell walls and vacuoles. Thus, foliar organic spraying impacted Hg enrichment in plant through altering plant physiological and biochemical indices, soil environment and Hg methylation processes.

H2 O2 , NO, and H2 S networks during root development and signalling under physiological and challenging environments: Beneficial or toxic?

Hydrogen peroxide (H₂ O₂ ) is a reactive oxygen species (ROS) and a key modulator of the development and architecture of the root system under physiological and adverse environmental conditions. Nitric oxide (NO) and hydrogen sulphide (H₂ S) also exert myriad functions on plant development and signalling. Accumulating pieces of evidence show that depending upon the dose and mode of applications, NO and H₂ S can have synergistic or antagonistic actions in mediating H₂ O₂ signalling during root development. Thus, H₂ O₂ -NO-H₂ S crosstalk might essentially impart tolerance to elude oxidative stress in roots. Growth and proliferation of root apex involve crucial orchestration of NO and H₂ S-mediated ROS signalling which also comprise other components including mitogen-activated protein kinase, cyclins, cyclin-dependent kinases, respiratory burst oxidase homolog (RBOH), and Ca²⁺ flux. This assessment provides a comprehensive update on the cooperative roles of NO and H₂ S in modulating H₂ O₂ homoeostasis during root development, abiotic stress tolerance, and root-microbe interaction. Furthermore, it also analyses the scopes of some fascinating future investigations associated with strigolactone and karrikins concerning H₂ O₂ -NO-H₂ S crosstalk in plant roots.

Signaling mechanisms and biochemical pathways regulating pollen-stigma interaction, seed development and seedling growth in sunflower under salt stress

Sunflower (Helianthus annuus L.) is one of the major oilseed crops cultivated world over for its high-quality oil rich in linoleic acid. It also has established applications in pharmaceutical and biotechnological industries, mainly through recombinant production of unique oil body (OB) membrane proteins-oleosins, which are used for producing a wide variety of vaccines, food products, cosmetics and nutraceuticals. The present review provides a critical analysis of the progress made in advancing our knowledge in sunflower biology, ranging from mechanisms of pollen-stigma interaction, seed development, physiology of seed germination and seedling growth under salt stress, and finally understanding the signaling routes associated with various biochemical pathways regulating seedling growth. Role of nitric oxide (NO) triggered post-translational modifications (PTMs), discovered in the recent past, have paved way for future research directions leading to further understanding of sunflower developmental physiology. Novel protocols recently developed to monitor temporal and spatial distributions of various biochemicals involved in above-stated developmental events in sunflower, will go a long way for similar applications in plant biology in future.

Low levels of strigolactones in roots as a component of the systemic signal of drought stress in tomato

Strigolactones (SL) contribute to drought acclimatization in shoots, because SL-depleted plants are hypersensitive to drought due to stomatal hyposensitivity to abscisic acid (ABA). However, under drought, SL biosynthesis is repressed in roots, suggesting organ specificity in their metabolism and role. Because SL can be transported acropetally, such a drop may also affect shoots, as a systemic indication of stress. We investigated this hypothesis by analysing molecularly and physiologically wild-type (WT) tomato (Solanum lycopersicum) scions grafted onto SL-depleted rootstocks, compared with self-grafted WT and SL-depleted genotypes, during a drought time-course. Shoots receiving few SL from the roots behaved as if under mild stress even if irrigated. Their stomata were hypersensitive to ABA (likely via a localized enhancement of SL synthesis in shoots). Exogenous SL also enhanced stomata sensitivity to ABA. As the partial shift of SL synthesis from roots to shoots mimics what happens under drought, a reduction of root-produced SL might represent a systemic signal unlinked from shootward ABA translocation, and sufficient to prime the plant for better stress avoidance.