Impact of lead and zinc heavy metal pollution on the growth and phytoremediation potential of Sulla carnosa in Sebkha el Kalbia, Tunisia

Heavy metal pollution from human and natural activities poses significant environmental and health concerns for wildlife and humans, with lead and zinc being particularly threatening. This study focuses on Sebkha el Kalbia in Tunisia, highlighting the challenges faced by local communities in addressing heavy metal pollution. The area is prone to contamination through rivers and streams that transport pollutants from industrial zones and rural areas into the salt pan. The recent establishment of an industrial zone has worsened pollution levels, calling for strict regulatory measures and clean technologies to limit heavy metal pollution and protect human health and the environment. The study assesses the impact of lead and zinc pollution on the growth of Sulla carnosa and its potential for phytoremediation. Soil and plant samples from contaminated areas were analyzed, revealing high levels of heavy metal contamination. The growth parameters of Sulla carnosa, such as plant height, weight, and enzymatic activity, were examined, showing a significant reduction in plant growth when exposed to high metal concentrations. Specifically, in the presence of 100 ppm of lead (Pb), net photosynthetic assimilation (An) decreased by 52%, while the amount of Pb increased by 78%. At 800 ppm of Pb, An decreased by 87%, and the amount of Pb increased by over 800%. Furthermore, the relationship between net photosynthetic assimilation and lead (Pb) content remained significant but negative. At high doses (800 ppm), the biomass produced decreases by 64%, while the amount of Zn increases 2.7 times. These results suggest that at low doses, zinc is not toxic. These findings highlight Sulla carnosa as a potential candidate for phytoremediation with preferential metal accumulation in the roots and improved enzymatic activity, underscoring the urgency of addressing heavy metal pollution in Sebkha el Kalbia.

Measurement of Algal Photosynthesis Using a Clark-Type O2 Electrode

The Clark-type electrode can be used to assess the rates of photosynthesis by detecting changes in O2 concentration in a culture. This chapter describes a method for a liquid phase measurement of light and dissolved inorganic carbon-dependent photosynthesis using the model green alga Chlamydomonas reinhardtii. The technique can be used to evaluate the presence or efficiency of carbon-concentrating mechanisms.

Modelling coastal upwelling off NW Iberian Peninsula: New insights on the fate of phytoplankton blooms

The northwestern coast of the Iberian Peninsula is a region characterized by pronounced hydrologic and biogeochemical activity, resulting in important fish and shellfish resources whose exploitation has a strong local socioeconomic impact. This high biological diversity is strongly dependent on coastal upwelling induced by favourable winds, which presents seasonal variability. This motivates the present study, which aims to understand the relation between local circulation, hydrography and Chl-a concentration under summer upwelling events of different intensities and clarify their effects in the region. To achieve this purpose, a coupled physical-biological model was developed and validated for the northwestern coast of the Iberian Peninsula, based on the use of MOHID modelling system and the application of a nested domains methodology. Comparison of predictions with observations demonstrated the model's accuracy in reproducing the physical and biogeochemical properties of the study region, both at the surface and along the water column. The study of different summer upwelling events shows that the local phytoplankton patterns are dependent on the characteristics of the event. Results show that under high upwelling favourable winds, a surface southwestward flow and an equatorward flow through the water column develop near the coast, inducing offshore advection of nutrient and phytoplankton-rich waters. Otherwise, under light upwelling favourable winds, surface currents are weak, a poleward flow develops, and phytoplankton is retained near the coast.

Foliar chlorophyll concentration modulates the degree of fungal exploitation in a rhizoctonia-associated orchid

Some green orchids obtain carbon from both mycobionts and photosynthesis at the adult stage. Intriguingly, these orchids can produce albino and, in rare cases, variegated phenotypes. Here, we studied a Platanthera hondoensis population with green, variegated, and albino individuals. Although its closely related Platanthera species are usually associated with non-ectomycorrhizal rhizoctonias, and several studies have failed to find evidence of trophic plasticity in rhizoctonia-associated orchids, variegated and albino P. hondoensis must possess a higher fungal dependency than green P. hondoensis. Therefore, we investigated whether (i) P. hondoensis is associated with non-ectomycorrhizal rhizoctonias and (ii) the degree of mycoheterotrophy (using 13C abundance as a proxy) correlates with the foliar chlorophyll concentration. High-throughput DNA sequencing revealed that all P. hondoensis phenotypes were dominantly associated with a rhizoctonia from Ceratobasidiaceae belonging to a clade distinct from recognized ectomycorrhizal clades. Regression analysis revealed a positive linear relationship between foliar chlorophyll concentration and the degree of mycoheterotrophy. This study strongly suggests that rhizoctonia-associated P. hondoensis can dynamically adjust fungal exploitation in response to photosynthetic carbon levels. Since rhizoctonia is the most common orchid mycorrhizal partner, trophic plasticity may be a widespread adaptive trait in green orchids.

Impact of catchment-derived nutrients and sediments on marine water quality on the Great Barrier Reef: An application of the eReefs marine modelling system

Water quality of the Great Barrier Reef (GBR) is determined by a range of natural and anthropogenic drivers that are resolved in the eReefs coupled hydrodynamic - biogeochemical marine model forced by a process-based catchment model, GBR Dynamic SedNet. Model simulations presented here quantify the impact of anthropogenic catchment loads of sediments and nutrients on a range of marine water quality variables. Simulations of 2011-2018 show that reduction of anthropogenic catchment loads results in improved water quality, especially within river plumes. Within the 16 resolved river plumes, anthropogenic loads increased chlorophyll concentration by 0.10 (0.02-0.25) mg Chl m^-3. Reductions of anthropogenic loads following proposed Reef 2050 Water Quality Improvement Plan targets reduced chlorophyll concentration in the plumes by 0.04 (0.01-0.10) mg Chl m^-3. Our simulations demonstrate the impact of anthropogenic loads on GBR water quality and quantify the benefits of improved catchment management.

Desert-adapted fungal endophytes induce salinity and drought stress resistance in model crops

Abiotic stresses are among the most damaging and ever-increasing threats to crop production worldwide. Utilizing extreme-habitat-adapted symbiotic microorganisms is a well-known strategy to mitigate the destructive effects of abiotic stresses on agricultural products. Here, we show the effects of the inoculation of halotolerant endophytic fungi recovered from desert plants on drought and salinity stress tolerance in two model agricultural plants A Periconia and two Neocamarosporium species were selected for this study after an in vitro halotolerant assay. Then, a random block design with three factors including fungi, salinity, and drought treatments was used to investigate the ability of these endophytes to induce stress resistance in tomato and cucumber plants. Physiological markers including proline content and activities of superoxide dismutase, catalase and peroxidase enzymes; as well as growth parameters and chlorophyll contents were assessed in all model plants. Fungal symbiosis increased chlorophyll concentration and plant growth, under all levels of salinity and drought stress. In model plants associated with P. macrospinosa significant increase in proline content and antioxidant enzymatic activities was observed under all levels of the salinity and drought stresses compared to the endophyte-free plants, while plants associated with the two Neocamarosporium species, indicated significant increasing proline content and antioxidant enzymatic activities only in high levels of the salinity and drought stresses. Our findings provide novel insights into the eco-physiological mechanisms of halotolerant fungal endophyte-mediated drought and salinity stress tolerance in cucumber and tomato plants, which signify the prospective applications of arid and saline habitat adapted endophytes in agricultural systems.

Spad value varies with age and leaf of maize plant and its relationship with grain yield

OBJECTIVES

A field experiment was conducted to evaluate Soil Plant Analysis Development (SPAD) value in different age and leaf of maize hybrid and correlating with grain yield. Ten maize hybrids were replicated thricely under Randomized Complete Block Design (RCBD) during winter of 2018. SPAD value was measured by SPAD 502 plus meter. At 30 days interval during vegetative stage SPAD measurement were taken from T1 (top most leaf) and T3 (2nd leaf from top leaf) leaves of five randomly selected plants from one plot and they were averaged. For reproductive phase data taken from eo (leaf attached to ear) and e2 (2nd leaf from eo leaf) leaves at 10 days intervals. Same leaves were used for entire data collection.

RESULTS

Significantly different SPAD value was observed for different age and leaves of maize during pre and post anthesis. SPAD value increase with increase in age and decrease at the time of maturity. During vegetative phase T3 leaves has more SPAD value than T1. During reproductive stage eo leaves had more SPAD than e2 leaves, so center leaf of maize contributes more to grain yield. Correlation showed that there is strong positive correlation between different stage of SPAD with grain yield.

Estimation of underwater visibility in coastal and inland waters using remote sensing data

An optical method is developed to estimate water transparency (or underwater visibility) in terms of Secchi depth (Z _sd ), which follows the remote sensing and contrast transmittance theory. The major factors governing the variation in Z _sd , namely, turbidity and length attenuation coefficient (1/(c + K _d ), c = beam attenuation coefficient; K _d  = diffuse attenuation coefficient at 531 nm), are obtained based on band rationing techniques. It was found that the band ratio of remote sensing reflectance (expressed as (R _rs (443) + R _rs (490))/(R _rs (555) + R _rs (670)) contains essential information about the water column optical properties and thereby positively correlates to turbidity. The beam attenuation coefficient (c) at 531 nm is obtained by a linear relationship with turbidity. To derive the vertical diffuse attenuation coefficient (K _d ) at 531 nm, K _d (490) is estimated as a function of reflectance ratio (R _rs (670)/R _rs (490)), which provides the bio-optical link between chlorophyll concentration and K _d (531). The present algorithm was applied to MODIS-Aqua images, and the results were evaluated by matchup comparisons between the remotely estimated Z _sd and in situ Z _sd in coastal waters off Point Calimere and its adjoining regions on the southeast coast of India. The results showed the pattern of increasing Z _sd from shallow turbid waters to deep clear waters. The statistical evaluation of the results showed that the percent mean relative error between the MODIS-Aqua-derived Z _sd and in situ Z _sd values was within ±25%. A close agreement achieved in spatial contours of MODIS-Aqua-derived Z _sd and in situ Z _sd for the month of January 2014 and August 2013 promises the model capability to yield accurate estimates of Z _sd in coastal, estuarine, and inland waters. The spatial contours have been included to provide the best data visualization of the measured, modeled (in situ), and satellite-derived Z _sd products. The modeled and satellite-derived Z _sd values were compared with measurement data which yielded RMSE = 0.079, MRE = -0.016, and R ²  = 0.95 for the modeled Z _sd and RMSE = 0.075, MRE = 0.020, and R ²  = 0.95 for the satellite-derived Z _sd products.

Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana

Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways.

Common gas phase molecules from fungi affect seed germination and plant health in Arabidopsis thaliana

Fungal volatile organic compounds (VOCs) play important ecophysiological roles in mediating inter-kingdom signaling with arthropods but less is known about their interactions with plants. In this study, Arabidopsis thaliana was used as a model in order to test the physiological effects of 23 common vapor-phase fungal VOCs that included alcohols, aldehydes, ketones, and other chemical classes. After exposure to a shared atmosphere with the 23 individual VOCs for 72 hrs, seeds were assayed for rate of germination and seedling formation; vegetative plants were assayed for fresh weight and chlorophyll concentration. All but five of the VOCs tested (1-decene, 2-n-heptylfuran, nonanal, geosmin and -limonene) had a significant effect in inhibiting either germination, seedling formation or both. Seedling formation was entirely inhibited by exposure to 1-octen-3-one, 2-ethylhexanal, 3-methylbutanal, and butanal. As assayed by a combination of fresh weight and chlorophyll concentration, 2-ethylhexanal had a negative impact on two-week-old vegetative plants. Three other compounds (1-octen-3-ol, 2-ethylhexanal, and 2-heptylfuran) decreased fresh weight alone. Most of the VOCs tested did not change the fresh weight or chlorophyll concentration of vegetative plants. In summary, when tested as single compounds, fungal VOCs affected A. thaliana in positive, negative or neutral ways.