New Insight into Short Time Exogenous Formaldehyde Application Mediated Changes in Chlorophytum comosum L. (Spider Plant) Cellular Metabolism

Chlorophytum comosum L. plants are known to effectively absorb air pollutants, including formaldehyde (HCHO). Since the metabolic and defense responses of C. comosum to HCHO are poorly understood, in the present study, biochemical changes in C. comosum leaves induced by 48 h exposure to exogenous HCHO, applied as 20 mg m^-3, were analyzed. The observed changes showed that HCHO treatment caused no visible harmful effects on C. comosum leaves and seemed to be effectively metabolized by this plant. HCHO application caused no changes in total chlorophyll (Chl) and Chl a content, increased Chl a/b ratio, and decreased Chl b and carotenoid content. HCHO treatment affected sugar metabolism, towards the utilization of sucrose and synthesis or accumulation of glucose, and decreased activities of aspartate and alanine aminotransferases, suggesting that these enzymes do not play any pivotal role in amino acid transformations during HCHO assimilation. The total phenolic content in leaf tissues did not change in comparison to the untreated plants. The obtained results suggest that HCHO affects nitrogen and carbohydrate metabolism, effectively influencing photosynthesis, shortly after plant exposure to this volatile compound. It may be suggested that the observed changes are related to early HCHO stress symptoms or an early step of the adaptation of cells to HCHO treatment. The presented results confirm for the first time the direct influence of short time HCHO exposure on the studied parameters in the C. comosum plant leaf tissues.

Fluctuating Asymmetry in Morphological Characteristics of Betula Pendula Roth Leaf under Conditions of Urban Ecosystems: Evaluation of the Multi-Factor Negative Impact

The fluctuating asymmetry (FA) in Betula pendula Roth was estimated as an integrated measure of five morphometric characteristics of a lamina. Samples were collected in seven cities that differ both in climatic conditions, moderately to sharply continental. In total, 33 ecotopes were distinguished with various level of anthropogenic load. The statistical data processing involved correlation, one-way and factorial ANOVA, regression analyses, and principal component analysis (PCA). The impact of 25 climatic and anthropogenic factors on the FA value was considered. In most urban ecotopes, the integrated fluctuating asymmetry (IFA) value was higher than in natural biotopes of the same region. No significant inter-annual differences in IFA values were found. FA dependence on traffic load is noted to be statistically significant. The covariation analysis of IFA, climatic, and anthropogenic variables in various urban ecotopes revealed the impact of three groups of factors that together explain 93% of the variance in environmental parameters. The complex analysis clearly arranged the studied ecotopes by pollution gradient and climatic patterns. The primary effect of the total anthropogenic load on the developmental stability of B. pendula results in an IFA increase. IFA can play a key role in bioindication assessment of environmental quality. The climatic factors have no significant effect on the developmental stability of B. pendula in urban conditions.

Estimating the frequency of hormesis and other non-monotonic responses in plants experiencing road traffic pollution in urban areas and experimental pollutant exposure

Various plant traits are widely utilised to assess environment health. However, non-monotonic responses in plants (hormesis and non-hormetic ones) can induce an incorrect assessment of contamination level because they have maximums and/or minimums. Hence, an increase in the pollution level will not always be accompanied by plant index deteriorations. The frequencies of non-monotonic responses, especially non-hormetic responses, have been insufficiently studied for plant traits. This study analysed the frequencies of non-monotonic changes in plants experiencing urban chemical pollution (B. pendula, T. cordata and T. officinale) and with different pollutant exposures (heavy metals, herbicide glyphosate, formaldehyde and sodium chloride) in experiments (T. aestivum and P. sativum). In the city, we evaluated the traits in plants with the same ontogenetic stages on plots near roads with various traffic and similar abiotic conditions. In urban areas, non-monotonic responses were found in both woody (B. pendula and T. cordata) and herbaceous (T. officinale) species for most traits. Their frequencies corresponded to the proportion of monotonic responses (B. pendula) or were even higher (T. cordata and T. officinale). In studied trees, non-monotonic responses were more common in biochemical traits compared with non-biochemical ones. With experimental pollutant exposure, non-monotonic responses were obtained for most traits of both dicotyledonous (P. sativum) and monocotyledonous (T. aestivum) plants, and their frequency was significantly higher than for monotonic ones. Non-hormetic responses significantly prevailed among non-monotonic changes of plant indexes in the city and experiments. Thus, it is necessary to consider both hormesis and non-hormetic responses to assess correctly environmental quality using plant indexes.

Change of Leaf Trait Asymmetry Type in Tilia cordata Mill. and Betula pendula Roth under Air Pollution

Leaf fluctuating asymmetry (FA) is widely used as an environmental stress index, including pollution. Besides FA, leaf bilateral traits can have directional asymmetry (DA) and antisymmetry (AS), which are considered hereditary. Leaf FA transitioning to DA/AS or mixed asymmetry, under air pollution, has been insufficiently investigated. This study analysed leaf asymmetry types in Tilia cordata Mill. and Betula pendula Roth under traffic air pollution over several years. In addition, the relations of such transitions to pollution, and their effect on FA-integrated index, were studied. The asymmetry types of all studied leaf traits varied with air pollution increase, as well as in control trees in different years. T. cordata most often had FA transition to DA/mixed asymmetry, while B. pendula rarely had a mixed asymmetry and FA transitions to DA/AS were observed with the same frequency. Air pollution impacted FA transitions to other asymmetry types. In most cases their frequency changed non-monotonically that corresponded to hormesis and paradoxical effects. However, FA integrated index in studied trees did not depend on change of leaf asymmetry type. Thus, DA and AS in studied plants were not exclusively hereditary. Hence, the changes of leaf asymmetry type should be considered when using leaf FA in environment assessment.

Hormesis and paradoxical effects of pea (Pisum sativum L.) parameters upon exposure to formaldehyde in a wide range of doses

Formaldehyde is a widespread pollutant of soil near roads including agricultural lands. Non-monotonic changes (hormesis and paradoxical effects) in chlorophyll (Ch) and carotenoid (Car) contents, the lipid peroxidation (LP) rate in plant leaves and growth parameters (GP) of plants can be caused by various pollutants. Hormesis is a biphasic dose-response phenomenon, characterised by low-dose stimulation and high-dose inhibition. The remaining types of non-monotonic responses are classified as paradoxical effects. While most authors who have studied formaldehyde and plants considered gaseous exposure to shoots, the effect of this pollutant in soil solution has been poorly examined. Thus, we studied the non-monotonic changes in Ch and Car contents, LP rate and GP in pea (Pisum sativum L.) upon exposure to formaldehyde in solution, at a wide range of sublethal concentrations from 0.063 × 10-2 to 0.16 g L-1. With formaldehyde exposure, LP and Ch contents had paradoxical effects (triphasic and multiphase changes, accordingly), while Car level did not change and GP exhibited a hormetic response. The date showed that pea parameters display diverse types of non-monotonic responses upon exposure to the same formaldehyde concentrations. High pollutant concentrations (0.08-0.16 g L-1) increased LP and significantly decreased GP (to 2.3-2.5 times compared to the control), while the Ch content was increased. Lower concentrations (<0.08 g L-1) caused a moderate deviation in all parameters from the control (not more than 62%) for hormesis and paradoxical effects.

Dependence of Guaiacol Peroxidase Activity and Lipid Peroxidation Rate in Drooping Birch (Betula pendula Roth) and Tillet (Tilia cordata Mill) Leaf on Motor Traffic Pollution Intensity

Hormesis and paradoxical effects are frequently found for different plant parameters. These phenomena were also observed for lipid peroxidation (LP) rate at environmental pollution. However, the role of antioxidant enzymes, particularly guaiacol peroxidases (GPX), in a nonmonotonic variation in the LP rate remains insufficiently explored. Therefore, dependence of GPX activity and LP rate in Betula pendula and Tilia cordata leaf on motor traffic pollution intensity was studied. Regression analysis revealed dependences of LP rate and GPX activity on traffic intensity. In B pendula, GPX activity enhanced significantly (up to 2.8 times relatively control) under increased traffic that induced biphasic paradoxical effect for LP rate. In the first phase, LP level increased in comparison with the control, and in the second phase, it was normalized by enhanced GPX activity. In T cordata, dependences of GPX activity and LP rate on traffic pollution were paradoxical effects. However, there was no connection between change of GPX activity and LP rate under middle- and high-level pollution: LP level reduced relatively the control or normalized even if GPX activity was lower than the control. This indicates that in T cordata, other regulatory mechanisms instead of GPX were activated which could control LP rate under middle- and high-level pollution.

Hormesis and Paradoxical Effects of Drooping Birch (Betula pendula Roth) Parameters Under Motor Traffic Pollution

Various plant indexes are used or recommended for bioindication. However, the nonmonotonic dose-response dependences (hormesis and paradoxical effects) of these indexes are insufficiently explored upon exposure to pollution. We studied the dependences of these Betula pendula indexes on the intensity of motor traffic pollution. Regression analysis did not reveal any dependence of chlorophyll and carotenoid content on traffic intensity (in 2008 and 2010-2013). Lipid peroxidation rate had different versions of paradoxical effects in 2008 and 2010 to 2012 and increased in comparison with control under an increase in pollution level in 2013. In 2010 to 2012, all dose-response dependences for total protein and thiol group content were biphasic and multiphasic paradoxical effects. In 2013, an increase in traffic intensity induced a linear reduction in protein content and an increase in thiol group level in comparison with the control. In most cases, the studied phenological indexes and seed production decreased monotonically in comparison with the control following an increase in traffic intensity. Only in 2010 and 2013, share of fallen leaves had hormesis and paradoxical effect accordingly. Fluctuating asymmetry had a paradoxical effect and hormesis in 2008 and 2012, accordingly, and increased in comparison with the control under an increase in the level of pollution in 2010 to 2011.