Nano Zinc-Oxide Enhanced Photosynthetic Apparatus and Photosystem Efficiency of Maize (Zea Mays L.) in Sandy-Acidic Soils

Conventional Zinc (Zn) fertilization (e.g., zinc sulfate) often leads to poor availability in soils. Zinc oxide nanoparticles (nano ZnO) can be a potential solution, but their effect on crop photosynthetic activity isn’t well documented. The effects of nano ZnO (50, 100, 150, 200 mg L-1) and application methods (seed-coating, soil-drench, and foliar-spray) in comparison with ZnSO4 recommended dose were evaluated for plant height, biomass, chlorophyll pigments and photosystem efficiency in a greenhouse pot experiment. 100 mg L-1 of nano ZnO significantly increased the chlorophyll (Chl.) a, b, a+b, carotenoids (x+c), a+b/x+c, SPAD, leaf Chl., total chlorophyll content plant-1, plant height and total biological yield (by 18-30%, 33-67%, 22-38%, 14-21%, 14-27%, 12-19%, 12-23% 58-99%, 6-11% and 16-20%, respectively) and reduced Chl. a/b (by 6-22%) over the other treatments (p<0.01) irrespective of application methods. Nano ZnO applied at 100 mg L-1 significantly increased photochemical quenching (qP) and efficiency of photosystem II (EPSII) compared to 150 and 200 mg L-1 regardless of application methods. The positive correlations between Chl. a and Chl. b (r2 0.90), Chl. a+b and x+c (r2=0.71), SPAD and Chl. a (r2=0.90), SPAD and Chl. b (r2=0.94) and SPAD and Chl. a+b (r2=0.93) indicates a uniform enhancement in chlorophyll pigments; SPAD value, qP, EPSII, and growth and yield parameters. This elucidates that the application of nano ZnO at 100 mg L-1 promotes corn biochemical health and photosynthesis, irrespective of the application method. These findings have a great propounding for improving plant growth through nano ZnO bio-fortification in acidic Spodosols.

In Vitro Morphophysiological Responses of Alternanthera Tenella Colla (Amaranthaceae) to Stress Induced by Cadmium and the Attenuating Action of Silicon

Despite having the ability to bioaccumulate trace elements such as cadmium (Cd), many species also present morphophysiological disorders that can hamper their use as phytoremediation plants. Since it can lead to alterations in biomass accumulation. The employment of elements that mitigate stress, such as silicon (Si), can diminish the deleterious effects caused by trace elements. The objective of this study was to analyze the anatomical and physiological modulations induced by the synergy between Cd and Si in Alternanthera tenella plants, as well as to elucidate whether Si can mitigate the harmful effects caused by Cd under in vitro conditions. Nodal segments were cultured in media containing a concentration gradient of Cd (0, 50, 100, or 200 μM) combined with two levels of Si (0 or 40 μM) for a total of eight treatments. After 34 days, the plants' anatomy, physiology, and tolerance index were analyzed. The plants presented anatomical adjustments (such as lower stomatal index and number of vessel elements), suggesting lower translocation of Cd to the aerial part. When cultured with 200 μM Cd, the plants presented the lowest Chl a/b ratio. In the presence of Si, the decline of this ratio was smaller. Plants exposed to Cd concentrations of 50 μM without Si presented a significant decrease in the performance of the photosynthetic apparatus and tolerance index. The presence of Si in the medium reduced the damages caused by cadmium to the plants' physiology, resulting in greater growth and higher tolerance to this element.

APPLICATION OF OJIP CHLOROPHYLL FLUORESCENCE TRANSIENT ANALYSIS TO STUDY THE POSTHARVEST CHANGES IN PHOTOSINTHETIC APPARATUS IN CUT FOLIAGE SPECIES

Chlorophyll fluorescence (ChlF) is a non-invasive technique that can be potentially used in postharvest research to gain useful information on early responses to postharvest stresses. This study was conducted to validate the application of ChlF transient analysis in determining the postharvest changes in photosynthetic apparatus in three ornamental foliage species, i.e., Cordyline fruticosa ‘Willy’s Gold’ and ‘Rubra’, Dracaena sanderiana ‘White’, and Nephrolepis exaltata. Salicylic acid (100 and 300 mg·L−1), glucose (10 g·L−1), and their combinations were used as holding solutions with control treatment (distilled water) at room temperature (25±2°C). Vase life was evaluated using OJIP analysis. OJIP parameters, i.e., specific energy fluxes per reaction center (ABS/RC, TR/RC, ET/RC, and DI/RC), flux ratios (maximum quantum yield of primary photochemistry-φPo), electron transport efficiency (ψo), and quantum yield of electron transport (φEo), and performance index (PI) were recorded every other day, using a fluorometer (FluorPen 100). Leaf chlorophyll contents of all species and anthocyanin contents of two cordyline cultivars were determined. Data were subjected to ANOVA in a completely randomized design. Mean separation was done by DMRT (p ≤ 0.05). Clear variations in ChlF were observed in every foliage species with the time. OJIP analysis showed species-depended variations. The higher ABS/RC and DI/RC were recorded for D. sanderiana and N. exaltata compared to the PI of those species. At the end of the experiment, the chlorophyll contents were decreased, while anthocyanin contents were increased. Consequently, chlorophyll fluorescence changes in photosynthetic apparatus can be used for the prediction of the postharvest stresses and longevity of cut foliage.

A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals

This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-1, Pb = 180 mg. Kg-1), double (Ag = 50 mg. Kg-1, Pb = 360 mg. Kg-1) and triple (Ag = 75 mg. Kg-1, Pb = 540 mg. Kg -1) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

The Effect of the Application of Stimulants on the Photosynthetic Apparatus and the Yield of Winter Wheat

The use of stimulation preparations seems to be a promising means for mitigating the effects of abiotic and biotic stressors. Their significance includes plant organism stimulation and metabolism optimisation, water regime, and nutrition during periods of stress. They help bridge it over and create conditions for rapid regeneration. In a field experiment, the effect of the application of stimulation preparations on cultivars Triticum aestivum L. with different genetic composition was evaluated (donor of blue aleurone colour KM-72-18; donor of a multi-row spike (MRS) KM-94-18). Our results show a predominantly positive effect of the application of stimulants on the yield and thousand-grain weight (TKW). The results obtained were influenced by the year, based on different temperatures and precipitation. Higher yields were achieved in 2020 with higher total precipitation during the grain filling period and with a higher maximum quantum yield of the photosystem II (Fv/Fm). In 2019, this period was significantly dry and warm, which was reflected in a lower yield and TKM, higher proline content in the leaves, and lower Fv/Fm values. In both experimental years, there was a higher yield of the cultivar with blue aleurone (KM-72-18). In the case of cultivars with coloured grains, the promising use of the content substances in cultivars as natural means of increasing resistance to abiotic and biotic stressors seems to be promising.

Diagnosis of the functional state of the photosynthetic apparatus Taraxacum officinale (L.) Weber ex F. H. Wigg. by the method of chlorophyll fluorescence induction

The informativeness is established of the method of induction of chlorophyll fluorescence for bioindication in the conditions of anthropogenic influence on the example of T. officinale plants, by the parameters: F0, Fm, Fst, Fv, Fv/Fm та k1, k2. The main parameters of the induction curve can be used as test indicators to determine the resistance of plants to adverse factors. Changes in these indicators characterize the processes associated with the influence of the environment on the course of both light and dark phases of photosynthetic processes in chloroplasts. The photosensitivity of T. offic- inale leaves, which indicates the physiological state of plants, decreases with increasing adverse external influences. It is established that the plants of T. officinale have the maximum intensity of photosynthesis, which grow in more favorable ecological conditions control. Therefore, the use of the device «Floratest» to determine the condition of plants at different levels of anthropogenic load is promising and requires further research.

Effect of Drought and Heavy Metal Contamination on Growth and Photosynthesis of Silver Birch Trees Growing on Post-Industrial Heaps

Silver birch trees (Betula pendula Roth) are a pioneering species in post-industrial habitats, and have been associated with an expansive breeding strategy and low habitat requirements. We conducted ecophysiological and dendroclimatological studies to check whether there are any features of which the modification enables birch trees to colonise extreme habitats successfully. We characterised the efficiency of the photosynthetic apparatus, the gas exchange, the content of pigments in leaves, and the growth (leaf thickness and tree-ring width) of birch trees on a post-coal mine heap, a post-smelter heap, and a reference site. Birch growth was limited mainly by temperature and water availability during summer, and the leaves of the birch growing on post-industrial heaps were significantly thicker than the reference leaves. Moreover, birch trees growing on heaps were characterised by a significantly higher content of flavonols and anthocyanins in leaves and higher non-photochemical quenching. In addition, birches growing on the post-coal mine heap accumulated a concentration of Mn in their leaves, which is highly toxic for most plant species. Increasing the thickness of leaves, and the content of flavonols and anthocyanins, as well as efficient non-photochemical quenching seem to be important features that improve the colonization of extreme habitats by birches.