Heavy metals (HMs) contamination poses a significant threat to environmental matrices, particularly soil, which is essential for food security, agricultural productivity, and key ecosystem services. Understanding how crops respond to HMs is crucial for developing biomonitoring strategies to assess soil contamination and inform remediation efforts. Plants, including crops, exhibit a range of functional traits (FT) that can indicate HMs stress and contamination levels. In this study, we investigated the response strategies of Zea mays L. var. Limagrain 31455, widely cultivated throughout the region of Land of Fires, a critically polluted area of southern Italy, to different concentrations of Zn, Pb, and Cr, corresponding to moderate to severe soil contamination. Functional traits related to the photosynthetic machinery, including gas exchange, chlorophyll fluorescence and reflectance indices, were examined. Root morpho-histochemical analysis were also conducted to correlate early root alterations with any observed changes in these photosynthetic traits. Results revealed distinct response patterns: tolerance to Zn, without adverse effects on photosynthetic traits; resistance to Pb, mediated by increased RD and photoprotection through change in reflectance indices; and sensitivity to Cr highlighted by severe functional impairments of all the studied photosynthetic traits and structural root damages. Functional traits, such as chlorophyll fluorescence parameters and the photochemical reflectance index or normalized difference vegetation index, demonstrated high potential for monitoring HMs stress responses; in addition, morpho-anatomical traits of the root system provided insights into biomass allocation and the capacity of var. Limagrain 31455 to tolerate and adapt to HMs stress. These findings underscore the importance of integrating physiological, anatomical, and spectral analyses to improve the biomonitoring and management of polluted soils and detecting spatial variability in contamination via remote sensing.

Heliotropium L. genus belongs to the Boraginaceae family and is represented by approximately 250 species found in the temperate warm regions of the world, and there are 15 species of these species recorded in Turkiye. Heliotropium hirsutissimum Grauer grows in Bulgaria, Greece, N. Africa, Syria, and Turkiye. There is no record showing that H. hirsutissimum is a heat-tolerant plant. However, in our field studies, it was observed that H. hirsutissimum, which is also distributed in Hisaralan Thermal Springs of Sindirgi-Balikesir, Turkiye, grows in the thermal area with extremely high soil temperature (57.6 degrees C (similar to 60 degrees C)). It was thought that it would be useful to investigate the tolerance mechanism of the H. hirsutissimum plant to extremely high temperatures. For this purpose, the plant seeds were obtained from a geothermal area in the thermal spring. Growing plants were exposed to 20, 40, 60, and 80 +/- 5 degrees C soil temperature gradually for 15 days under laboratory conditions. We measured the effect of high soil temperature on some morphological changes, relative water content, thiobarbituric acid reactive substances, cell membrane stability, and hydrogen peroxide analysis to determine stress levels on leaves and roots. Changes in osmolyte compounds, some antioxidant enzyme activities, ascorbate content, and chlorophyll fluorescence and photosynthetic gas exchange parameters were also determined. As a result of the study carried out to determine the stress level, it was observed that there was not much change and it was understood that the plant was tolerant to high soil temperature. In addition, there was a general increase in osmolytes accumulation, antioxidant enzyme activities, and ascorbate level. There was no significant difference in photosynthetic gas exchange and chlorophyll fluorescence parameters of plants grown at different soil temperatures. The high temperature did not negatively impact the photosynthetic yield of H. hirsutissimum because this plant was found to enhance its antioxidant capacity. The increase in antioxidant activity helped reduce oxidative damage and protect the photosynthetic mechanism under high temperature conditions, while the significant increase in the osmolyte level helped maintain the water status and cell membrane integrity of plants, thus enabling them to effectively withstand high soil temperatures.

Tetracycline (TC) antibiotics are one of the class of drugs widely used in clinical practice but also constitute a significant environmental concern. However, the adverse effects of TC on non-target organisms have not been well studied. The aim of this study was to examine the influence of exposure to high levels of TC on thalli of lichens to determine the impact on (1) physiological parameters including integrity of cell membranes, photosynthetic efficiency and viability, (2) oxidative stress response such as membrane lipid peroxidation, and (3) enzymatic antioxidant activities as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). Data demonstrated that exposure to tetracycline did not markedly affect the lichen membrane damage as indicated by no change in conductivity. This antibiotic diminished the potential photosystem II efficiency (FV/FM) indicating enhanced susceptibility as evidenced by lower chlorophyll fluorescence and chlorophyll content. The viability of lichens exposed to high concentrations of tetracycline was significantly reduced. The concentrations of thiobarbituric acid reactive substances were markedly elevated with increasing concentrations of antibiotics. At higher TC concentrations, 500 mg/L SOD activity was significantly elevated. In the case of CAT, APX and GR, TC at higher concentrations significantly decreased these enzymic activities. The findings of this study contribute to the knowledge that TC antibiotics exert adverse ecotoxicological effects on lichens at high concentrations and provided a better understanding of the mechanisms underlying toxicity. Data also indicates that lichens may serve as an effective biomonitoring species for TC antibiotic exposure.

Water deficit has a negative effect on the physiological aspects of plants, such as stomatal closure and consequent decline in photosynthetic carbon assimilation. Numerous water deficit mitigation strategies have been investigated, such as the use of bioregulators to minimize the damage caused. This study aimed at assessing the effects of brassinosteroids on the physiological aspects of a & ccedil;a & iacute; seedlings in inducing drought tolerance. The experiment was conducted using two water conditions (well-watered and water-deficit plants) and three brassinosteroid concentrations (0, 0.05 and 0.10 mu M of 24-epibrassinolide-EBL), with six repetitions. At 120 days, seedlings were transplanted to pots and watered, leaving the soil near field capacity for 56 days. Next, a group of plants were well-watered, and another submitted to water deficit for 18 days. Water deficit reduced gas exchange and photosynthetic efficiency with a lower decrease at EBL concentrations of 0.05 and 0.10 mu M, while larger declines were observed in plants without EBL. Relative water content and leaf succulence were maintained in water-deficit plants, while proline content rose, mainly with 0.10 mu M of EBL. Applying EBL also improved water use efficiency and maintained the leaf chlorophyll and stem dry matter of stressed plants. It was concluded that leaf brassinosteroid application alleviate of harmful effects of water deficit in young a & ccedil;a & iacute; plants, promoting proline accumulation, which increases water use efficiency, and maintaining photosynthetic pigments and water status, contributing to improving drought tolerance in a & ccedil;a & iacute;.

In recent decades, flash drought events have frequently occurred in the humid regions of southern China. Due to the sudden onset and rapid intensification of these droughts, they often cause severe damage to vegetation photosynthesis. However, our understanding of the spatiotemporal evolution characteristics of flash droughts across different vegetation types, as well as the response regularity of photosynthesis to flash droughts, especially early responses, remains limited. This study analyzes the spatiotemporal evolution characteristics of flash droughts for different vegetation types in the Middle and Lower Reaches of the Yangtze River Basin from 2000 to 2023. It uses solar-induced chlorophyll fluorescence (SIF) and fluorescence yield (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{{\upvarphi\:}}_{\text{F}\:}$$\end{document}) to explore the response regularity of vegetation photosynthesis to flash droughts, with a systematic analysis of the 2013 flash drought event. The results show that, over the past 24 years, the frequency of flash droughts for different vegetation types in the Middle and Lower Reaches of the Yangtze River Basin has decreased, but the total duration has increased, with forests experiencing the highest frequency of flash droughts, while cropland experiences the least. Cropland photosynthesis is the most sensitive to flash drought, showing an early response 8-16 days after the onset and reaching a negative anomaly between 24 and 32 days. Forests mainly show an early response between 16 and 24 days and a negative anomaly response between 32 and 40 days. During the 2013 flash drought, cropland showed an early response on the 10th day after the onset and a negative anomaly on the 26th day, while forest responses were later, with early responses on the 20th day and negative anomalies on the 36th day. These results align with long-term statistical data. This study contributes to a deeper understanding of vegetation photosynthesis response regularity to flash droughts and provides insights for developing effective flash drought management strategies.

Salvia splendens Ker-Gawl. (scarlet sage), widely used in urban landscaping, it is frequently exposed to cadmium (Cd) contamination resulting from industrial and vehicular emissions. However, its tolerance and adaptability to Cd stress remain poorly understood. A soil experiment was conducted to investigate the effects of Cd on the growth and the photosynthetic performance of S. splendens by measuring photosynthetic pigments, gas exchange and chlorophyll fluorescence parameters. Four weeks-seedlings were treated with 0 (CK), 0.5, 2.5, 5, 10, 25 and 50 mgkg(-1) Cd for 60 days. Results showed significant reductions in root length and biomass of leaves, stems, and roots, with shoot and root biomass notably decreasing by up to 46.3% and 28.5% at higher Cd levels, respectively. The translocation factor remained low (TF 5 mgkg(-1)) caused a decrease in Chl a and Chl b content, but increased the Chl a/b ratio, thereby disrupting photosynthesis and causing significant declines in photosynthetic parameters. Cd exposure (> 2.5 mgkg(-1)) significantly decreased net photosynthetic rate (Pn) by 18.94-52.91%, stomatal conductance (Gs) by 35.77-58.53%, and transpiration rate (Tr) by 24.63-48.83%, accompanied by only a slight reduction in inter-cellular CO2 concentration (Ci) of just 7.0%, indicating non-stomatal factors in Pn decline. Cd concentrations (> 5 mgkg(-1)) caused a reduction in initial fluorescence (Fo) by 7.44-31.58% and maximal fluorescence (Fm) measurements by about 20%, indicating damage to photosystem II (PSII). At 50 mgkg(-1), further decreases were observed in photochemical quenching (qP) by 40.31%, the quantum yield of photochemical energy dissipation (Phi PSII) by 44.77%, and the electron transport rate (ETR) by 25.11%, while non-photochemical quenching increased by 42.66%, signifying significant PSII inhibition and enhanced photoinhibition. Decrease in Phi PSII, along with the increase in the quantum yield of regulated non-photochemical energy loss in PSII (Phi NPQ) and the quantum yield of non-regulated energy loss in PSII (Phi NO) as Cd levels rise, indicates enhanced non-photochemical energy dissipation and greater photoinhibition. S. splendens shows high sensitivity to Cd stress, with reduced growth and disrupted photosynthesis, highlighting its potential as a bioindicator for Cd contamination in urban areas.

Ability of remotely sensed solar-induced chlorophyll fluorescence (SIF) to serve as a vegetation productivity and stress indicator is impaired by confounding factors, such as varying crop-specific canopy structure, changing solar illumination angles, and SIF-soil optical interactions. This study investigates two normalisation approaches correcting diurnal top-of-canopy SIF observations retrieved from the O2-A absorption feature at 760 nm (F 760 hereafter) of summer barley crops for these confounding effects. Nadir SIF data was acquired over nine breeding experimental plots simultaneously by an airborne imaging spectrometer (HyPlant) and a drone-based highperformance point spectrometer (AirSIF). Ancillary measurements, including leaf pigment contents retrieved from drone hyperspectral imagery, destructively sampled leaf area index (LAI), and leaf water and dry matter contents, were used to test the two normalisation methods that are based on: i) the fluorescence correction vegetation index (FCVI), and ii) three versions of the near-infrared reflectance of vegetation (NIRV). Modelling in the discrete anisotropic radiative transfer (DART) model revealed close matches for NIRv-based approaches when corrected canopy SIF was compared to simulated total chlorophyll fluorescence emitted by leaves (R2 = 0.99). Normalisation with the FCVI also performed acceptably (R2 = 0.93), however, it was sensitive to variations in LAI when compared to leaf emitted chlorophyll fluorescence efficiency. Based on the results modelled in DART, the NIRvH1 normalisation was found to have a superior performance over the other NIRv variations and the FCVI normalisation. Comparison of the SIF escape fractions suggests that the escape fraction estimated with NIRvH1 matched escape fraction extracted from DART more closely. When applied to the experimental drone and airborne nadir canopy SIF data, the agreement between NIRvH1 and FCVI produced chlorophyll fluorescence efficiency was very high (R2 = 0.93). Nevertheless, NIRvH1 showed higher uncertainties for areas with low vegetation cover indicating an unaccounted contribution of SIF-soil interactions. The diurnal courses of chlorophyll fluorescence efficiency for both approaches differed not significantly from simple normalisation by incoming and apparent photosynthetically active radiation. In conclusion, SIF normalisation with NIRvH1 more accurately compensates the effects of canopy structure on top of canopy far red SIF, but when applied to top of canopy in-situ data of spring barley, the effects of NIRvH1 and FCVI on the diurnal course of SIF had a similar influence.

Rising soil salinity poses significant challenges to Mediterranean viticulture. While some rootstocks effectively reduce salt accumulation in grafted scions, the mechanisms and performance of novel rootstocks remain largely unexplored. This study compared two novel M-series rootstocks (M2, M4) with established commercial rootstocks (1103 Paulsen, R110) to evaluate their physiological responses and salt tolerance under irrigation with varying salinity levels (0, 25, 50, and 75 mM NaCl) over 5 months. Growth parameters, photosynthetic efficiency, chlorophyll content (SPAD), ion homeostasis, and visual symptoms were monitored. Results revealed genotype-specific strategies: 1103 Paulsen exhibited robust photosynthetic efficiency and ion exclusion, maintaining growth and chlorophyll stability; M2 demonstrated superior biomass retention and moderate ion compartmentalization but showed reduced photosynthetic performance at higher salinity levels; R110 displayed effective ion management at moderate salinity but experienced significant growth reduction under severe stress; and M4 was the most sensitive, with severe reductions in growth and ion homeostasis. Organ-specific responses highlighted roots acting as primary ion reservoirs, particularly for sodium and calcium; leaves exhibited high potassium and chloride concentrations, critical for photosynthesis but prone to ionic imbalance under stress; and stems and wood played a buffering role, compartmentalizing excess sodium and minimizing damage to photosynthetic tissues. The reported findings provide valuable insights for rootstock selection and breeding programs, particularly for regions facing increasing soil and water salinization challenges.

Understanding the distribution of plant moisture during the seedling stage of greenhouse crops is challenge in developing scientific irrigation strategies and proposing effective cooling methods. This study investigated the effects of different soil moisture contents [W1: 25-35 % (severe drought), W2: 35-45 % (mild drought), W3: 45-55 % (suitable moisture), and W4: 55-65 % (excess moisture)] on tomato seedlings under summer greenhouse thermic extremes. Furthermore, thermal infrared imaging and chlorophyll fluorescence multi-dimensional digital image sensors were used to determine differences in tomato seedling morphology and plant physiology. The increase in canopy area under W1 and W4 soil moisture content was smaller than that of W2 and W3, and the canopy area of the W1 group decreased as the high temperature condition continued. The average canopy temperature of each treatment generally increased first, and then plateaued. From high to low, average temperatures were 28.15 degrees C in W1, 27.73 degrees C in W4, 26.67 degrees C in W2, and 25.72 degrees C in W3. The canopy temperature gradually decreased from the middle to the edge of the leaf (stem temperature > leaf base temperature > leaf vein temperature > leaf edge temperature). The F-v/F-m ratio in the chlorophyll fluorescence index qualitatively expresses the degree of water stress. phi PSII, non-photochemical quenching (NPQ), and qP values were used as indicators to quantitatively analyze stress in leaves of different maturity. A preliminary mathematical relationship between the canopy and NPQ was established. This study quantitatively characterized the morphological and physiological changes of tomato seedlings in the greenhouse during summer, visualized the process of canopy temperature changes, and provided a theoretical basis for mitigating heat-induced damage.

Polyamines (PAs) are signaling molecules that exhibit promising roles in improving stress tolerance in plants. Limited information is available concerning the effects of the exogenous PAs on medicinal plants including chamomile. This experiment was carried out to study the effects of foliar application of PAs [Putrescine (Put), Spermidine (Spd), and Spermine (Spm)] on physiological and biochemical processes to understand the possible mechanisms concerning the water deficit stress [soil Field Capacity (FC) as control, 80% of FC (FC80), and 60% of FC (FC60)] alleviation in German Chamomile. We found that PAs partially inhibited water deficit-induced stomatal closure and induced antioxidant enzymes to eliminate the increased H2O2. Spd increased stomatal conductance (g(s)) by 66, 65, and 35% at FC, FC80, and FC60, respectively, compared with the control. The increased g(s) enhanced leaf net photosynthesis (A(N)) by 52 and 86% at FC80 and FC60, respectively, compared with the control. The role of PAs in oxidative damage alleviation was approved by the negative correlation of leaf antioxidant activities and Malondialdehyde (MDA) and H2O2 content. According to the results, PAs function as stress-protecting compounds to instigate the antioxidative enzymes to scavenge stress-induced H2O2, improve membrane stability, and enhance water deficit tolerance. Generally, our results suggested that PAs could be potential growth regulators to alleviate mild to severe water deficit stress.