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Various physiological and biochemical responses of two good biomonitor plant species i.e. Datura alba and Ricinus communis were studied along two roads in the Punjab, Pakistan. Chlorophyll a , b , total chlorophylls, carotenoids, total free amino acids, total soluble proteins, total antioxidant activity, stomatal conductance, photosynthetic rate, internal CO 2 concentration, transpiration rate, and water use efficiency of D. alba and R. communis were examined at different sites along both roads. Photosynthetic rate of both plant species was found to be affected. Reduced transpiration rate and stomatal conductance were also noted. However, elevated internal CO 2 concentration and water use efficiency were recorded. Total soluble proteins got reduced, but, we found a tremendous increase in total antioxidant activity and total free amino acids in both plant species. D. alba was found to be more affected by the adverse effects of roadside air borne pollutants. Although R. communis was also affected but it showed minimal variation in all parameters compared to the control. Hence, our results suggest that R. communis is more resistant to urban roadside air pollution compared to D. alba and would be a good choice as phytoremediator of traffic borne pollutants, whereas, D. alba could be a better biomonitoring plant. • Vehicle exhaust is the biggest sources of air pollution these days. • Biological effects of vehicle pollution can be assessed by the use of biomonitoring plants. • R. communis and D. alba are two effective biomonitoring plants. • They responded differently to vehicle exhaust pollution at roadsides. • R. communis could be a good phytoremediator, while, D. alba can be used as a bioindicator plant at roadsides. [ABSTRACT FROM AUTHOR]

Castor (Ricinus communis L.) is an important oilseed crop worldwide, and is also considered as one of the most promising plants for alkali-affected soil amelioration in the northeast of China. Seed germination plays a vital role in seedling establishment, and is always sensitive to alkali stress. However, little is known about the dynamic changes and regulatory mechanisms of gene expression and metabolic processes of this species during germination stage under alkali stress. In the present study, physiological, metabolome and transcriptome responses in germinating seeds of castor were investigated when exposed to 0, 50, 100 and 150 mM alkalinity (NaHCO 3). The results showed that alkali stress sharply decreased germination percentage. The Na+ content increased but K+ content decreased under alkalinity. In addition, the malondialdehyde and proline contents increased with the increasing alkalinities. Meanwhile, 50, 100 and 150 mM alkalinity induced 31, 48 and 113 differential metabolites, respectively. Furthermore, transcriptome profiling result showed that there were 138, 845 and 694 differentially expressed genes in the seeds under different concentrations alkali stresses, respectively. The integrating analysis of metabolite and gene expression changes indicating that germination response of castor seeds under alkali stress was closely related to amino acid metabolism, carbohydrate metabolism, lipid metabolism and nucleotide metabolism. The adaptive strategies of castor seeds under alkaline stress were promoting amino acid metabolism and tricarboxylic acid cycle to regulate osmotic balance and ROS level; as well as providing materials and energy for secondary metabolism, although alkali stress affected the membrane fluidity due to the reduction of unsaturated fatty acid content. Moreover, castor seeds increased metabolites on nucleotide biosynthesis to ensure their germination process under alkaline salt stress. The present research provides a deeper insight into overall understanding alkali-tolerant mechanisms of oil crops during germination in a holistic level. • l Using metabolomics and transcriptomics explored physiological adaptation mechanisms of castor seeds under alkali stress. • l 31, 48 and 113 differential metabolites and 138, 845 and 694 differentially expressed genes were found under alkali stress. • l Germination of castor at alkalinity was closely related to amino acid, carbohydrate, lipid and nucleotide metabolisms. • l Seeds of castor promoted amino acid metabolism and tricarboxylic acid cycle under stress. l Seeds of castor provided materials and energy for secondary metabolism under stress. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stomatal closure and osmotic adjustment are key physiological responses to salt stress displayed by R. communis. [•] Na+ and Cl− effectively participate in the osmotic adjustment of R. communis to salinity. [•] The contribution to the osmotic adjustment of Na+ was higher in leaves, while roots contributed to the Cl− osmotic adjustment more effectively. [ABSTRACT FROM AUTHOR]

Abstract: Castor plants (Ricinus communis) cv. BRS Nordestina were submitted to biweekly defoliations in order to evaluate the influence on development and yield components. Leaf area was calculated from the length of the main vein of each leaf. Defoliation treatments of 0, 15, 30, 45 or 60% of the total leaf area were applied. Each raceme was individually harvested and the date was recorded. Castor plants were able to completely regrow its leaf area when the defoliation occurred during the vegetative stage; however, this initial damage reduced the maximum leaf area obtained by the plant. Maturation of fruits occurred earlier when plants were subjected to defoliation. Defoliation treatments did not influence the number of fruits per raceme, but caused a steep reduction of the number of racemes per plant. Adaptations in the yield components were observed in the number of seeds per plant and in the seed oil content, but not in the mean seed weight. Any level of defoliation repeated along the plant growth cycle was found to cause a reduction of the oil yield. The loss of 1m2 of leaf area caused the reduction of 37.8g of castor seed or 24.4g of castor oil. [ABSTRACT FROM AUTHOR]