Comparison of Ion Balance and Nitrogen Metabolism in Old and Young Leaves of Alkali-Stressed Rice Plants

BACKGROUND: Alkali stress is an important agricultural contaminant and has complex effects on plant metabolism. The aim of this study was to investigate whether the alkali stress has different effects on the growth, ion balance, and nitrogen metabolism in old and young leaves of rice plants, and to compare functions of both organs in alkali tolerance. METHODOLOGY/PRINCIPAL FINDINGS: The results showed that alkali stress only produced a small effect on the growth of young leaves, whereas strongly damaged old leaves. Rice protected young leaves from ion harm via the large accumulation of Na(+) and Cl(-) in old leaves. The up-regulation of OsHKT1;1, OsAKT1, OsHAK1, OsHAK7, OsHAK10 and OsHAK16 may contribute to the larger accumulation of Na(+) in old leaves under alkali stress. Alkali stress mightily reduced the NO(3)(-) contents in both organs. As old leaf cells have larger vacuole, under alkali stress these scarce NO(3)(-) was principally stored in old leaves. Accordingly, the expression of OsNRT1;1 and OsNRT1;2 in old leaves was up-regulated by alkali stress, revealing that the two genes might contribute to the accumulation of NO(3)(-) in old leaves. NO(3)(-) deficiency in young leaves under alkali stress might induce the reduction in OsNR1 expression and the subsequent lacking of NH(4)(+), which might be main reason for the larger down-regulation of OsFd-GOGAT and OsGS2 in young leaves. CONCLUSIONS/SIGNIFICANCE: Our results strongly indicated that, during adaptation of rice to alkali stress, young and old leaves have distinct mechanisms of ion balance and nitrogen metabolism regulation. We propose that the comparative studies of young and old tissues may be important for abiotic stress tolerance research

Climate change : strategies for mitigation and adaptation

The sustainability of life on Earth is under increasing threat due to humaninduced climate change. This perilous change in the Earth's climate is caused by increases in carbon dioxide and other greenhouse gases in the atmosphere, primarily due to emissions associated with burning fossil fuels. Over the next two to three decades, the effects of climate change, such as heatwaves, wildfires, droughts, storms, and floods, are expected to worsen, posing greater risks to human health and global stability. These trends call for the implementation of mitigation and adaptation strategies. Pollution and environmental degradation exacerbate existing problems and make people and nature more susceptible to the effects of climate change. In this review, we examine the current state of global climate change from different perspectives. We summarize evidence of climate change in Earth’s spheres, discuss emission pathways and drivers of climate change, and analyze the impact of climate change on environmental and human health. We also explore strategies for climate change mitigation and adaptation and highlight key challenges for reversing and adapting to global climate change

Effects of alkali stress on the expression (relative units) of genes involved in NH₄⁺ assimilation in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates, and each replicate consisted of a pool of 10 plants. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p

Effects of alkali stress on the growth in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p

Effects of alkali stress on the contents of organic acids (OA) and soluble sugars in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates, and each replicate consisted of a pool of 10 plants. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p

Additional file 2: of The emergence of DNA in the RNA world: an in silico simulation study of genetic takeover

gt1-dx. This file is an executable version of our simulation interface program, which has been tested under the platform of MS-Windows XP and MS-Windows 7.0. (EXE 3434 kb

Effects of alkali stress on the expression of <i>OsAKT1</i> and <i>OsHAK</i> gene family in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates, and each replicate consisted of a pool of 10 plants. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p

Effects of alkali stress on the expression (relative units) of <i>OsAMT</i> and <i>OsNRT</i> gene families in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates, and each replicate consisted of a pool of 10 plants. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p

Effects of alkali stress on the contents of inorganic ions in young and old leaves of rice seedlings.

<p>The values are means (± SE) of four biological replicates, and each replicate consisted of a pool of 10 plants. Statistically significant between organs at same stress condition was determined by <i>t</i>-test, and marked as * (<i>P</i><0.05) and ** (<i>P</i><0.01). The seedlings were subjected to 50 mM alkali stress (NaHCO₃∶Na₂CO₃ = 9∶1; pH 9.10) stresses for 6d.</p