Brief exposure to low-pH stress causes irreversible damage to the growing root in Arabidopsis thaliana: pectin-Ca interaction may play an important role in proton rhizotoxicity

Sodium Chloride (NaCl)-Induced Physiological Alteration and Oxidative Stress Generation in Pisum sativum (L.): A Toxicity Assessment

Salinity stress has a deleterious impact on plant development, morphology, physiology, and biochemical characteristics. Considering the NaCl-induced phytotoxicity, current investigation was done to better understand the salt-tolerant mechanisms using Pisum sativum L. (pea) as a model crop. Generally, NaCl resulted in a progressive decrease in germinative attributes and physiological and biochemical parameters of P. sativum (L.). The 400 mM NaCl level had a higher detrimental effect and reduced the germination rate, plumule, radicle length, and seedling vigor index (SVI) by 78, 89, 84, and 77%, respectively, under in vitro. Furthermore, after 400 mM NaCl exposure, physiological and enzymatic profiles like root dry biomass (71%) chl-a (66%), chl-b (54%), total chlorophyll (45%), and nitrate reductase activity (NRA) (59%) of peas were decreased. In addition, a NaCl dose-related increase in soluble protein (SP) and sugar (SS), Na⁺ and K⁺ ions, and stressor metabolites was recorded. For instance, at 400 mM NaCl, SP, SS, Na⁺ ion, K⁺ ion, root proline, and malondialdehyde (MDA) contents were significantly and maximally elevated by 65, 33, 84, 79, 85, and 89%, respectively, compared to the control (0 mM NaCl). Data analysis indicated that greater doses of pesticides dramatically increased reactive oxygen species (ROS) levels and induced membrane damage through production of thiobarbituric acid reactive substances (TBARS), as well as increased cell injury. To deal with NaCl-induced oxidative stress, plants subjected to higher salinity stress showed a considerable build-up in antioxidant levels. As an example, ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were maximally and significantly (p ≤ 0.05) increased by 68, 80, 74, and 58%, respectively, after 400 mM NaCl exposure. The propidium iodide (PI)-stained and NaCl-treated plant roots corroborated the damaging effect of salinity-induced stress on the cell membrane, which was observed under a confocal laser microscope (CLSM). The cells exposed to 400 mM NaCl had maximum fluorescence intensity, indicating that higher level of salts can cause pronounced cell damage and reactive oxygen species (ROS) generation. The increases in superoxide ion (O₂ ^-) and hydrogen peroxide (H₂O₂) content in NaCl-treated plant tissues indicated the elevation of ROS with increasing salt levels. This finding revealed that salt stress can cause toxicity in plants by causing alteration in metabolic activity, oxidative injury, and damage to cell membrane integrity.

ESTUDOS DA TOXICIDADE DO ALUMÍNIO EM VALORES DE pH 7,0 E 7,5 PARA BRASSICA OLERACEA L. E RAPHANUS SATIVUS L

A toxicidade do alumínio tem sido verificada somente em valores de pH abaixo de 5,5 devido a solubilidade dos íons Al3+ que ocorre em meio ácido. Este trabalho teve o objetivo de estudar a toxicidade do alumínio em valores de pH 7,0 para a espécie Raphanus sativus L. (rabanete) e 7,5 para a Brassica oleracea L. (couve) com a finalidade de verificar se em tais valores de pH o alumínio não apresentava efeitos deletérios observáveis. Foi utilizada uma metodologia em que o meio de cultivo continha sementes como organismos testes e um rígido controle dos valores de pH. Os ensaios toxicológicos empregavam concentrações otimizadas de macro e micronutrientes necessários ao desenvolvimento das plântulas. Com o estudo foi possível verificar elevada Toxicidades Aguda e Crônica dos íons Al3+ em valores de pH 7,0 e 7,5 para as plantas estudadas, comprovando que os efeitos tóxicos do alumínio podem ser verificados também em meio de cultivo com valores de pH neutro e ligeiramente básico.