Effects of graft copolymer of chitosan and salicylic acid on reducing rot of postharvest fruit and retarding cell wall degradation in grapefruit during storage.

Salicylic acid (SA), as an enigmatic signalling molecule in plants, has been intensively studied to elucidate its role in defence against biotic and abiotic stresses. This review focuses on recent research on the role of the SA signalling pathway in regulating cadmium (Cd) tolerance in plants under various SA exposure methods, including pre-soaking, hydroponic exposure, and spraying. Pretreatment with appropriate levels of SA showed a mitigating effect on Cd damage, whereas an excessive dose of exogenous SA aggravated the toxic effects of Cd. SA signalling mechanisms are mainly associated with modification of reactive oxygen species (ROS) levels in plant tissues. Then, ROS, as second messengers, regulate a series of physiological and genetic adaptive responses, including remodelling cell wall construction, balancing the uptake of Cd and other ions, refining the antioxidant defence system, and regulating photosynthesis, glutathione synthesis and senescence. These findings together elucidate the expanding role of SA in phytotoxicology.

https://www.mdpi.com/1422-0067/20/12/2960/pdf

Salicylic Acid Signals Plant Defence against Cadmium Toxicity

Light is a key factor influencing growth and development in plants. Specific irradiance and light quality can improve development and production of secondary compounds such as carotenoids during plant tissue culture. Bixin and norbixin, two apocarotenoids obtained from the seeds of Bixa orellana L. (annatto), are used as natural dyes in various industries. While annatto tissue culture has been successful, the effect of light in this species remains poorly understood. Here, we analyze for the first time the effect of irradiance regime (50, 150, 50 + 150, 200, 50 + 200 μmol m−2 s−1) and light spectral quality (fluorescent, white, blue/red LED) on in vitro development of apexes and bixin content in two contrasting bixin-producing varieties of B. orellana, namely ‘Piave Vermelha’ and ‘UESB74’. The number of leaves per plant, stomatal density, leaf area, leaf expansion, chlorophylls and carotenoids content, malondialdehyde and bixin content were analyzed in the leaves of both cultivars. ‘Piave Vermelha’ produced 1.6-fold more bixin than ‘UESB74’. Stomata cells of both cultivars had a paracytic arrangement with peltate trichomes along the adaxial and abaxial leaf surfaces. ‘Piave Vermelha’ preferred blue/red LED light; whereas fluorescent light was optimal for ‘UESB74’. Under fluorescent light, an irradiance of 50 μmol m−2 s−1 is indicated for both cultivars. LED light increased bixin content only in ‘Piave Vermelha’, suggesting that the dye biosynthetic pathway is genotype-dependent. The present findings suggest the possibility of using light to modulate the bixin biosynthetic pathway.

Irradiance and light quality affect two annatto (Bixa orellana L.) cultivars with contrasting bixin production

Jasmonates (JAs), such as jasmonic acid and its methyl ester, are lipid-derived compounds with signal functions in plant growth and development, as well as in responses to stress. JAs are widely distributed in plants as natural plant growth regulators. JAs do not work independently but work as a part of a complex signaling network with other phytohormones. They are deployed to induce response during wounding and are often used for elicitation and stimulation of secondary metabolites production in different in vitro culture systems. Application of JAs seems to be promising during different steps of the micropropagation system for different species. JAs stimulate proliferation rate of shoots, roots, callus and induce microtubers and bulblets formation. However, negative effects of JAs on the condition of plant tissues are also reported, e.g. leaf senescence, reduced growth and inhibited somatic embryogenesis. This review summarizes the current knowledge of the application and properties of jasmonates under in vitro conditions in terms of cell division, explant growth, proliferation ability, storage organ formation and stress response. The review summarized in detail the results achieved for plants cultivated in vitro in the presence of jasmonates and their possible mechanisms of action.

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Role and activity of jasmonates in plants under in vitro conditions

Plants perform in a specific Eh–pH spectrum and they rely on various processes to ensure their homeostasis, which plays a central role in their defense. The effects of multiple stresses, all translated into oxidative stress into the plant, and the capacity of the latter to respond to these stresses results in specific Eh–pH states in plants. We reviewed plant-invertebrate pests and plant-pathogens interactions under a Eh–pH homeostasis perspective by extensively analyzing the literature, which converges and supports a set of hypotheses. We report examples showing how the development and attacks of pests are correlated to spatio-temporal variations of Eh–pH in plants. We provide evidence-based discussion on how Eh–pH homeostasis can open a new perspective on plant health, and help unravel and disentangle the many Genotype x Environment x Management x Pest and Pathogen interactions. We propose an original perspective on energy allocation and growth-defense tradeoff by plants based on the Eh–pH homeostasis model. Finally, we show how Eh–pH conditions in the rhizosphere are the results of multiple interactions between the root system and microorganisms. Based on this, we hypothesize that soil suppressiveness is derived from soil structure leading to diverse Eh–pH niches that harbor a diversity of microorganisms. The Eh–pH homeostasis model proposed herein is central to soil and plant health. An Eh–pH perspective could become a very powerful tool to develop a “one health approach” unifying a large range of bio-physical processes in a very coherent and consistent manner.

Soil and plant health in relation to dynamic sustainment of Eh and pH homeostasis: A review

Methyl jasmonate and salicylic acid are able to modify cell wall but only salicylic acid alters biomass digestibility in the model grass Brachypodium distachyon

Thiago Alves Napoleão

Papers

Methyl jasmonate and salicylic acid are able to modify cell wall but only salicylic acid alters biomass digestibility in the model grass Brachypodium distachyon