Physiological and biochemical analyses shed light on the response of <i>Sargassum vulgare</i> to ocean acidification at different time scales

Studies regarding macroalgal responses to ocean acidification (OA) are mostly limited to short-term experiments in controlled conditions, which hamper the possibility to scale up the observations to long-term effects in the natural environment. To gain a broader perspective, we utilized volcanic CO2 vents as a “natural laboratory” to study OA effects on Sargassum vulgare at different time scales. We measured photosynthetic rates, oxidative stress levels, antioxidant contents, antioxidant enzyme activities, and activities of oxidative metabolic enzymes in S. vulgare growing at a natural acidified site (pH 6.7) compared to samples from a site with current pH (pH 8.2), used as a control one. These variables were also tested in plants transplanted from the control to the acidified site and vice-versa. After short-term exposure, photosynthetic rates and energy metabolism were increased in S. vulgare together with oxidative damage. However, in natural populations under long-term conditions photosynthetic rates were similar, the activity of oxidative metabolic enzymes was maintained, and no sign of oxidative damages was observed. The differences in the response of the macroalga indicate that the natural population at the acidified site is adapted to live at the lowered pH. The results suggest that this macroalga can adopt biochemical and physiological strategies to grow in future acidified oceans

Contextualizing Statelessness in the Indian Legal Framework: Illegal Immigration in Assam

With the publication of the National Register of Citizens (NRC) in Assam, the indispensable question regarding the legal status of individuals who would be excluded from the final version arises. This paper critically analyzes the legal framework that addresses and governs statelessness, by taking into consideration, both the domestic laws, and the international treaties which India is a party to, and argues that the contemporary legal system does not address the issue of statelessness effectively and requires an overhaul. The lack of a comprehensive legislative policy to address statelessness will prevent uniformity in the expulsion methods that is employed by the state. In the light of forced deportation and the subsequent expulsion, this paper highlights the significance of formulating a uniform policy that operates on established humanitarian principles that does not vary from one instance to another

Quantitative analysis of venation patterns of Arabidopsis leaves by supervised image analysis

The study of transgenic Arabidopsis lines with altered vascular patterns has revealed key players in the venation process, but details of the vascularization process are still unclear, partly because most lines have only been assessed qualitatively. Therefore, quantitative analyses are required to identify subtle perturbations in the pattern and to test dynamic modeling hypotheses using biological measurements. We developed an online framework, designated Leaf Image Analysis Interface (LIMANI), in which venation patterns are automatically segmented and measured on dark-field images. Image segmentation may be manually corrected through use of an interactive interface, allowing supervision and rectification steps in the automated image analysis pipeline and ensuring high-fidelity analysis. This online approach is advantageous for the user in terms of installation, software updates, computer load and data storage. The framework was used to study vascular differentiation during leaf development and to analyze the venation pattern in transgenic lines with contrasting cellular and leaf size traits. The results show the evolution of vascular traits during leaf development, suggest a self-organizing mechanism for leaf venation patterning, and reveal a tight balance between the number of end-points and branching points within the leaf vascular network that does not depend on the leaf developmental stage and cellular content, but on the leaf position on the rosette. These findings indicate that development of LIMANI improves understanding of the interaction between vascular patterning and leaf growth

SHORT-ROOT and SCARECROW regulate leaf growth in Arabidopsis by stimulating S-phase progression of the cell cycle.

SHORT-ROOT (SHR) and SCARECROW (SCR) are required for stem cell maintenance in the Arabidopsis (Arabidopsis thaliana) root meristem, ensuring its indeterminate growth. Mutation of SHR and SCR genes results in disorganization of the quiescent center and loss of stem cell activity, resulting in the cessation of root growth. This paper reports on the role of SHR and SCR in the development of leaves, which, in contrast to the root, have a determinate growth pattern and lack a persistent stem cell niche. Our results demonstrate that inhibition of leaf growth in shr and scr mutants is not a secondary effect of the compromised root development but is caused by an effect on cell division in the leaves: a reduced cell division rate and early exit of the proliferation phase. Consistent with the observed cell division phenotype, the expression of SHR and SCR genes in leaves is closely associated with cell division activity in most cell types. The increased cell cycle duration is due to a prolonged S-phase duration, which is mediated by up-regulation of cell cycle inhibitors known to restrain the activity of the transcription factor, E2Fa. Therefore, we conclude that, in contrast to their specific roles in cortex/endodermis differentiation and stem cell maintenance in the root, SHR and SCR primarily function as general regulators of cell proliferation in leaves

Drought tolerance in selected aerobic and upland rice varieties is driven by different metabolic and antioxidative responses

Main conclusions: Sugar-mediated osmotic acclimation and a strong antioxidative response reduce drought-induced biomass loss at the vegetative stage in rice. Abstract: A clear understanding of the physiological and biochemical adaptations to water limitation in upland and aerobic rice can help to identify the mechanisms underlying their tolerance to low water availability. In this study, three indica rice varieties-IR64 (lowland), Apo (aerobic), and UPL Ri-7 (upland)-, that are characterized by contrasting levels of drought tolerance, were exposed to drought at the vegetative stage. Drought-induced changes in biomass, leaf metabolites and oxidative stress markers/enzyme activities were analyzed in each variety at multiple time points. The two drought-tolerant varieties, Apo and UPL Ri-7 displayed a reduced water use in contrast to the susceptible variety IR64 that displayed high water consumption and consequent strong leaf dehydration upon drought treatment. A sugar-mediated osmotic acclimation in UPL Ri-7 and a strong antioxidative response in Apo were both effective in limiting the drought-induced biomass loss in these two varieties, while biomass loss was high in IR64, also after recovery. A qualitative comparison of these results with the ones of a similar experiment conducted in the field at the reproductive stage showed that only Apo, which also in this stage showed the highest antioxidant power, was able to maintain a stable grain yield under stress. Our results show that different metabolic and antioxidant adaptations confer drought tolerance to aerobic and upland rice varieties in the vegetative stage. The effectiveness of these adaptations differs between developmental stages. Unraveling the genetic control of these mechanisms might be exploited in breeding for new rice varieties adapted to water-limited environments.</p