Little is known about how the characteristic differences in organ size between species are regulated. At the cellular level, the size of an organ is strictly regulated by cell division and expansion during its development. We performed a meta-analysis of the growth parameters of roots, and Graminae and eudicotyledonous leaves, to address the question of how quantitative variation in these two processes contributes to size differences across a range of species. We extracted or derived cellular parameters from published kinematic growth analyses. These data were subjected to linear regression analyses to identify the parameters that determine differences in organ growth. Our results demonstrate that, across all species and organs, similar conclusions can be made: cell number rather than cell size determines the final size of plant organs; cell number is determined by meristem size rather than the rate at which cells divide; cells that are small when leaving the meristem compensate by expanding for longer; mature cell size is primarily determined by the duration of cell expansion. These results identify the regulation of the transition from cell division to expansion as the key cellular mechanism targeted by the evolution of organ size.

The aim of the present work was to explore physiological changes provoked by somaclonal variation in response to salinity. Two parental cultivars (La Candelaria and Yerua) and their derived somaclones were used as a source for breeding new rice lines with improved salt tolerance. We studied the effect of NaCl salt stress on chlorophyll fluorescence-related parameters, such as the maximum quantum yield of primary PSII photochemistry (F v /F m ) and the performance index for energy conservation from photon absorbed by PSII antenna (PI ABS ). In addition malondialdehyde (MDA) content and leaf temperature (LT) responses were also measured. In somaclonal lines, F v /F m , PI ABS , MDA and LT showed coefficients of variation of 13.7, 39.3, 25.5, and 3 %, respectively, for La Candelaria and 1.4, 17.6, 34.4 and 3 % for Yerua. However, the fragrant character did not differ in the aromatic somaclonal lines with respect to their parentals. Our results suggest that the F v /F m ratio would not be as good marker of PSII vitality as PI ABS for salinized rice somaclones, unless they are highly susceptible to salinity. On other hand, the MDA content showed a strong negative correlation with the PI ABS content in somaclones of both rice cultivars, suggesting that MDA levels could also be used as an oxidative damage index in rice somaclones.

The physiological response of multiple rice cultivars, eighteen initially and eight cultivars later on, to suboptimal temperatures (ST) conditions was investigated in laboratory and outdoor experimental conditions. Treatment with ST decreased growth in different extents according to the cultivar and affected the PSII performance, determined by chlorophyll fluorescence fast‐transient test, and stomatal conductance, regardless the experimental condition. Two groups of cultivars could be distinguished on the base of their growth and physiological parameters. The group of cultivars presenting higher growths displayed optimal JIP values, and higher instantaneous water use efficiency (WUEi), due to a lower Gs under ST, unlike cultivars showing lower growth values, which presented worse JIP values and could not adjust their Gs and hence their WUEi. In this work, we detected at least two cultivars with superior tolerance to ST than the cold tolerant referent Koshihikari. These cultivars could be used as parents or tolerance donors in breeding for new crop varieties. On other hand, positive and significant correlations between data obtained from laboratory and outdoor experiments suggest that laboratory measurements of most of the above mentioned parameters would be useful to predict the response of rice cultivars to ST outdoor.

Polyamines (PAs) are natural aliphatic amines involved in many physiological processes in almost all living organisms, including responses to abiotic stresses and microbial interactions. On other hand, the family Leguminosae constitutes an economically and ecologically key botanical group for humans, being also regarded as the most important protein source for livestock. This review presents the profuse evidence that relates changes in PAs levels during responses to biotic and abiotic stresses in model and cultivable species within Leguminosae and examines the unreviewed information regarding their potential roles in the functioning of symbiotic interactions with nitrogen-fixing bacteria and arbuscular mycorrhizae in this family. As linking plant physiological behavior with “big data” available in “omics” is an essential step to improve our understanding of legumes responses to global change, we also examined integrative MultiOmics approaches available to decrypt the interface legumes-PAs-abiotic and biotic stress interactions. These approaches are expected to accelerate the identification of stress tolerant phenotypes and the design of new biotechnological strategies to increase their yield and adaptation to marginal environments, making better use of available plant genetic resources.

The lichenized green microalga Trebouxia lynnae Barreno has been recently described and is considered a model organism for studying lichen chlorobionts. Its cellular ultrastructure has already been studied in detail by light, electron, and confocal microscopy, and its nuclear, chloroplast and mitochondrial genomes have been sequenced and annotated. Here, we investigated in detail the ultrastructure of in vitro grown cultures of T. lynnae observed by Low Temperature Scanning Electron Microscopy (LTSEM) applying a protocol with minimum intervention over the biological samples. This methodology allowed for the discovery of ultrastructural features previously unseen in Trebouxiophyceae microalgae. In addition, original Transmission Electron Microscopy (TEM) images of T. lynnae were reinterpreted based on the new information provided by LTSEM. The nucleolar vacuole, dictyosomes, and endoplasmic reticulum were investigated and reported for the first time in T. lynnae and most likely in other Trebouxia lineages.

Background: Echinochrome A (EchA) is a pigment from sea urchins. EchA is a polyhydroxylated 1,4-naphthoquinone that contains several hydroxyl groups appropriate for free-radical scavenging and preventing redox imbalance. EchA is the most studied molecule of this family and is an active principle approved to be used in humans, usually for cardiopathies and glaucoma. EchA is used as a pharmaceutical drug. Methods: A comprehensive literature and patent search review was undertaken using PubMed, as well as Google Scholar and Espacenet search engines to review these areas. Conclusions: In the bloodstream, EchA can mediate cellular responses, act as a radical scavenger, and activate the glutathione pathway. It decreases ROS imbalance, prevents and limits lipid peroxidation, and enhances mitochondrial functions. Most importantly, EchA contributes to the modulation of the immune system. EchA can regulate the generation of regulatory T cells, inhibit pro-inflammatory IL-1β and IL-6 cytokine production, while slightly reducing IL-8, TNF-α, INF-α, and NKT, thus correcting immune imbalance. These characteristics suggest that EchA is a candidate drug to alleviate the cytokine storm syndrome (CSS).

This chapter focuses on polyamine biosynthesis, catabolism, and subcellular localization; effects of drought, salinity and cold stresses on polyamine level and enzymes involved in polyamine synthesis; role of polyamines and their synthesis inhibitors in plant response to drought, salininity and cold stress; effects of genetically altered polyamine levels on the improvement of plant stress tolerance; and mechanisms underlying polyamines-mediated drought, salinity and cold stress alleviation (membrane stabilization, and osmotic and ion homeostasis; antioxidant activity; polyamine interactions with hormones and other signal molecules and transcription factors; cell growth under salinity mediated by polyamine-catabolism-derived reactive oxygen species; and alteration of polyamine-level-mediated gene expression and stimulation of regulatory proteins phosphorylation).

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