Air mapping during COVID-19 and association between air pollutants and physiochemical parameters of the plants using structural equal modeling: a case study

In urban areas around the world, air pollution introduced by vehicular movement is a key concern. However, restricting vehicular traffic during the COVID-19 shutdown improved air quality to some extent. This study was conducted out in the smart city of Bhubaneswar, which is also the state capital of Odisha, India. The study has tried to map Bhubaneswar by collecting the air quality data before, during, and after the COVID lockdown of six air quality monitoring stations present in Bhubaneswar established under "National Ambient Air Monitoring Program" (NAMP). Furthermore, plants, which are the most vulnerable to air pollution, can show a variety of visible changes depending on their level of sensitivity. Moreover, leaves of Mangifera indica, Monoon longifolium, Azadirachta indica, Millettia pinnata, Aegle marmelos were collected from nearby of six air monitoring stations to assess the "Air Pollution Tolerance Index." M. indica was found to be intermediately tolerant, and all of the other species were found to be sensitive. The structural equation modeling results also revealed a significant relationship between total chlorophyll content, relative water content, ascorbic acid content, leaf extract pH, APTI with species, air quality index, and PM10.

Evaluation of air pollution (dust) tolerance index of three desert species Seidlitzia rosmarinus, Haloxylon aphyllum, and Nitraria schoberi under salinity stress

Dust causes adverse effects on the physiological and biochemical properties of plants, and under soil salinity conditions, these effects seem to be intensified, which limits their use in the development of the green belt around or within cities. In the research, the effect of salt (0, 30, and 60 dS m^-1) on air pollution (dust, 0 and 1.5 g m^-2 30 days^-1) tolerance index (APTI), peroxidase activity, and protein content of three desert species Seidlitzia rosmarinus, Haloxylon aphyllum, and Nitraria schoberi was investigated. The results indicated that the use of dust alone did not change the concentration of total chlorophyll in H. aphyllum, while it decreased the concentration of total chlorophyll by 18% in N. schoberi and 21% in S. rosmarinus. Under salt stress conditions, before and after applying dust, the concentration of total chlorophyll decreased in S. rosmarinus and N. schoberi plants, but there was no change in H. aphyllum. The amount of ascorbic acid, peroxide activity, and pH increased significantly with increasing salinity level before and after applying dust. Applying dust alone increased pH value only in N. schoberi and the amount of ascorbic acid and peroxidase in all three plants. Applying dust alone reduced relative water content and APTI only in N. schoberi plant and the amount of protein in all three plants. At salinity level of 60 dS m^-1 and with application of dust treatment, APTI was decreased by 10, 15, and 9% compared to its control before application of dust, respectively, in H. aphyllum, N. schoberi, and S. rosmarinus plants. Therefore, it was found that N. schoberi, which may be used as a bioindicator of air quality, has a lower APTI than S. rosmarinus and H. aphyllum, which may be served as suitable sinks to survive the air pollution (the development of a design on green belt around or within the city), under conditions of simultaneous application of dust and salt.

Grafting in Hylocereus (Cactaceae) as a tool for strengthening tolerance to high temperature stress

The Hylocereus species that are grown as exotic fruit crops are very often farmed under marginal agronomic conditions, which may include exposure to high temperatures. Here we present a pioneering investigation of grafting as an agro-technique to improve heat tolerance in Hylocereus. To this end, we studied the diploid species H. undatus, the tetraploid H. megalanthus and its di-haploid gamete-derived line 2719, and the interspecific-interploid tetraploid Z-10, all grafted onto H. undatus as the rootstock. Self-grafted, grafted and non-grafted plants were acclimated for one week (to obtain baseline values) and then exposed to heat stress (45/35 °C day/night) for three days, followed by a one-week recovery period under optimal temperatures (30/22 °C). A comparison of the physiological, biochemical and molecular performances of the grafted and self-grafted plants under heat stress and during the recovery period vs those of non-stressed plants (control; 30/22 °C) showed that the grafted and self-grafted plants performed better in most of the assessments: grafted and self-grafted plants recovered more rapidly from the heat stress and suffered far less stem damage. An unexpected - but important - finding that may have implications for other crop was that the self-grafted plants showed better performance than non-grafted plants throughout the trial. Our findings provide support for grafting as a strategy for coping with the stress induced by extremely high temperatures. This study thus paves the way for further investigations of grafting in Hylocereus as a valuable technique that will maintain crop productivity in the face of increasing worldwide temperatures.

Effect of phosphorus concentration on the photochemical stability of PSII and CO2 assimilation in Pistacia vera L. and Pistacia atlantica Desf

A greenhouse pot experiment was conducted at the faculty of sciences of Gafsa to evaluate the effect of phosphorus treatment on two pistachio species. The seedlings of Pistacia vera and Pistacia atlantica were subjected to six levels of phosphoric acid (P₂O₅) (0, 5, 15, 30, 60 and 120 ppm). Stomatal conductance, net photosynthesis, chlorophyll fluorescence (OJIP) and total chlorophyll content were measured after 1, 2, 3, 6, 8, 9 and 12 weeks of treatment. During the experiment, phosphorus application at 5 ppm increased photosynthesis and stomatal conductance, relative to the treatment 0 ppm only in P. atlantica. However, phosphorus supply at 60 and 120 ppm induced toxicity leading to an inhibition of CO₂ photo-assimilation rate, an alteration of photosystem II (PSII) structure and function and reduction in leaf chlorophyll content in both species. The (OJIP) transient showed complex changes in O-J, J-I and I-P phases of fluorescence. Due to phosphorus toxicity, both donor and acceptor sides of PSII were damaged, electron transport perturbed and chlorophyll pigment reduced which resulted in the fall of CO₂ photo-assimilation rate, followed by mortality in both species.

Chlorophyll extraction from suji leaf (Pleomele angustifolia Roxb.) with ZnCl2 stabilizer

Suji (Pleomele angustifolia Roxb.) leaves are a prominent source of chlorophyll and well-known for their ability to produce green color for food ingredients. However, chlorophyll is suspectible to color degradation at high temperature. Color degradation occurred because porphyrin loses magnesium in its ring and it can be avoided by adding zinc. The aim of this work was to investigate the combined effect of independent variables on chlorophyll extraction process using ZnCl₂ as a stabilizer. Suji leaves were blanched with boiling water for 2 min, Zn-chlorophyll synthesis was done by varying concentration of ZnCl₂, Zn-chlorophyll extraction with ethanol, and UV-Vis spectrophotometry analysis of the final extracted solutions. A full three-level factorial design under response surface methodology was used to obtain the optimum condition of extraction process. The experimental data were analyzed by analysis of variance and fitted with second order polynomial equation. The coefficient of determination (R²) was found to be 81.99%. The optimum operating conditions were obtained at pH 7, ZnCl₂ concentration of 700 ppm and temperature of 85 °C with desirability value of 1.0000. At the optimum conditions, the total chlorophyll content (TCC) was found to be 47.2975 mg/100 g fresh weight.

Pollution resistance assessment of existing landscape plants on Beijing streets based on air pollution tolerance index method

Various plant species of green belt in urban traffic area help to reduce air pollution and beautify the city environment. Those plant species growing healthily under long-term atmospheric pollution environment are considered to be resilient. This study aims to identify plant species that are more tolerant to air pollution from traffic and to give recommendations for future green belt development in urban areas. Leaf samples of 47 plant species were collected from two heavy traffic roadside sites and one suburban site in Beijing during summer 2014. Four parameters in leaves were separately measured including relative water content (RWC), total chlorophyll content (TCH), leaf-extract pH (pH), and ascorbic acid (AA). The air pollution tolerance index (APTI) method was adopted to assess plants' resistance ability based on the above four parameters. The tolerant levels of plant species were classified using two methods, one by comparing the APTI value of individual plant to the average of all species and another by using fixed APTI values as standards. Tolerant species were then selected based on combination results from both methods. The results showed that different tolerance orders of species has been found at the three sampling sites due to varied air pollution and other environmental conditions. In general, plant species Magnolia denudata, Diospyros kaki, Ailanthus altissima, Fraxinus chinensis and Rosa chinensis were identified as tolerant species to air pollution environment and recommend to be planted at various location of the city, especially at heavy traffic roadside.