Szilvia Veres

Effects of the available nitrogen on the photosynthetic activity and xanthophyll cycle pool of maize in field

Summary Investigations were performed on the interrelation between the photoprotective role of the xanthophyll cycle and levels of N-supply in maize plants ( Zea mays L. cv. Maya). Plants were grown in non-fertilised and fertilised plots, while the latter were supplied with 30, 60, 90, 120 and 150 kg ha −1 NH 4 NO 3 and grown under natural conditions in the field. The photosynthetic carbon assimilation of plants with higher N-supply, as compared to that of plants with lower N-supply, showed no significant differences, although a peak of the CO 2 assimilation rate was observed at 60 and 90 kg N ha −1 treatment levels. Maize plants with lower N-supply had a lower leaf Chl-content than plants with higher N-supply, which was accompanied by a reduced rate of photochemical efficiency of photosystem II and a high thermal energy dissipation activity, measured as non-photochemical fluorescence quenching. Plants supplied with lower doses of N were detected to have a greater fraction of xanthophyll cycle pool in the form zeaxanthin and antheraxanthin. With reduction of the N-supply levels an increase in the ratio of xanthophyll cycle pigments as related to total Chl was observed. These results suggest that with the decrease of N-supply there is an increasing need to dissipate the excess light energy in the chloroplasts of maize leaves through xanthophyll cycle.

Soil Salinisation and Salt Stress in Crop Production

For optimal grow and development, cultivated plants require balanced presence of water and dissolved minerals (salts) in their rhizosphere. In that respect, quality and availability of two natural resources, water and soils, are crucial in cultivation. Although Earth abounds in water, an almost negligible portion (~2.5% or 35 million km3) is fresh or with low salt concentration ( 90% in many developing countries) of total water withdrawal to produce ~36% of global food (Howell, 2001). According to recent estimates (ICID, 2009), almost 300 million ha in the world are irrigated, with ~2/3 of that in most populated and the fast growing Asian countries. In many irrigated agricultural areas, especially in developing countries, water scarcity is pronounced because of environmental conditions (e.g. arid and semiarid climate zones) and the rising population (i.e. food demand). As a consequence, there is an increasing trend of innappropriate use of restricted water (e.g. over/pumping of salinised aquifers) and continuous degradation of land resources (e.g. salt-affected soils), representing a large burden to human food supply and natural ecosystems. Some of the most produced and widely used crops in human/animal nutrition such as cereals (rice, maize), forages (clover) or horticultural crops (potatoes, tomatoes) usually require irrigation practices, but are relatively susceptible to excessive concentration of salts either dissolved in irrigation water or present in soil (rhizosphere) solution. In a majority of cultivated plants, yields start declining even at relatively low salinity in irrigation water (ECw>0.8 dS/m) (e.g. Ayers & Westcot, 1994) or soil (ECse>1 dS/m in saturated soil extracts) (see Table 1 in Chinnusamy et al., 2005). Increased soil salinity may induce various primary and secondary salt stress effects in cultivated plants (section 4.3.1). Salt stress as one of the most widespread abiotic constraints in food production may also result in the negative ecological, social and/or economic outcomes. For instance, recent deposition of toxic salt sediments and sea intrusion in tsunami-affected areas of Maldives damaged >70% of agriculture land, destroyed >370, 000 fruit trees and affected around 15, 000 farmers, with 2 costs estimated at around AU

Carotenoid composition and photochemical activity of four sandy grassland species

6.5 million (FAO, 2005). Successful remediation of saltdegraded areas for crop production, besides using relatively salt-tolerant species/genotypes, is highly dependent on sustainable management practices that are usually costly, time consuming and may be difficult or impossible to implement fully in certain ecological situations (e.g. seepage soil salinity ; section 3.1). Accordingly, in response to the salinity issue, Australia’s National Action Plan for Salinity and Water Quality from 2000, resulted in investments of about AU

Variations in leaf pigment content and photosynthetic activity of Phragmites australis in healthy and die-back reed stands of Lake Ferto/Neusiedlersee

1.4 billion over 7 years to support actions by communities and land managers in salt-affected regions (Williams, 2010). However, recent advances in plant breeding and molecular biology technologies suggest that increasing salt tolerance in cultivated plants could be one of the most promising and effective strategies for food production in salt-affected environments.

Effects of Biofertilizers on Maize and Sunflower Seedlings under Cadmium Stress

The photosynthetic pigments and photochemical efficiency of photosystem 2 (PS2) were studied in four constitutive species (Achillea millefolium L., Festuca pseudovina Hack. ex Wiesb., Potentilla arenaria Borkh., and Thymus degenianus Lyka) of a semiarid grassland in South-eastern Hungary. Every species displayed typical sun-adapted traits and substantial plasticity in the composition and functioning of the photosynthetic apparatus. The contents of chlorophylls (Chls) and carotenoids (Cars) on a dry matter basis declined from May to July, however, the amount of total Cars on a Chl basis increased. This increase was the largest in Potentilla (48 %) and the smallest in Achillea (14 %). The pool of xanthophylls (VAZ) was between 25 % and 45 % of the total Car content and was larger in July than in May. The content of β-carotene increased by July, but lutein content did not change significantly. The Chl fluorescence ratio Fv/Fm was reduced by 3–10 % at noon, reflecting the down-regulation of PS2 in the period of high irradiance and high temperature. The occurrence of minimal values of ΔF/Fm’ showed close correlation to the de-epoxidation rate of violaxanthin. Hence in natural habitats these species developed a considerable capacity to dissipate excess excitation energy in the summer period in their photosynthetic apparatus through the xanthophyll cycle pool and a related photoprotective mechanism, when the photochemical utilization of photon energy was down-regulated.

The effects of bio-fertilizers and nitrogen nutrition on the physiology of maize

The photosynthetic capacity of the common reed (Phragmites australis /Cav./ Trin. ex Steudel) was studied in various reed stands in the littoral zone of Lake Fertõ. Measurements were performed in three healthy and two dieback reed stands in the summer of 1997. In the leaves of declining reeds, the chlorophyll content was lower than in the vigorous sites. In the former sites, there was a significant rise in the total carotenoid pool (320–480 mmol mol−1chl (a + b)) as compared to that of the vigorous sites (250–350 mmol mol−1 chi (a + b). The size of the xanthophyll cycle pool and the β-carotene content of leaves significantly increased in the die-back sites. In early summer, the potential photochemical quantum efficiency of Photosystem II (Fv/Fm) did not differ considerably (0.79–0.81) from site to site, yet by August it significantly decreased (0.74–0.77) in the die-back sites as compared to the vigorous sites. The maximum CO2 assimilation rate measured on the 3rd and 4th leaves ranged from 11 to 17 CO2μmol m−2 s−1 and from 9 to 12 CO2μmol m−2 s−1 in the vigorous sites and the die-back sites, respectively. The stomatal conductance was also lower in the die-back sites (200–350 mmol H2O m−2 s−1) than in the vigorous reed stands (380–510 mmol H2O m−2s−1) which might result in the functional impairment of the gas ventilation system of the declining reeds, and consequently in oxygen deficiency and damage to the rhizome.

Comparison of Selenium Toxicity in Sunflower and Maize Seedlings Grown in Hydroponic Cultures.

Application of various alternative nutrient supplies can partly be substituted by chemical fertilizers, resulting in economical use with less environmental strains. Biofertilizers containing living microorganisms promote nutrition uptake, but still there are questions regarding their application under stress conditions. One of the main abiotic factors that can induce stress is contamination of soils with toxic elements. In the course of intensive plant-growth conditions, considerable quantities of basic cations are removed from the soil, resulting in acidification and thereby enhancing the uptake of heavy metals by plants. Cadmium (Cd) toxicity is a major problem affecting crop productivity worldwide. The presence of Cd in the rhizosphere can cause stress responses and alteration in many physiological processes, including nitrogen metabolism, photosynthesis, carbohydrate metabolism, sulfate assimilation, and plant–water interactions. Once in the plant, Cd can enter the food chain, causing public health problems. The aim of our work was to investigate the effects of biofertilizers on plant production and nutrient uptake in some Cd-contaminated soils. Our results revealed that Cd accumulated primarily in the roots and transport to the shoots was rather low; however, there were differences between the two plants species. Plant uptake by sunflower was greater than by maize, and sunflower appeared to be more stress tolerant of Cd than maize. With the use of the bacterium-containing biofertilizer, the toxic effect of Cd was moderated.

Biological changes of green pea (Pisum sativum L.) by selenium enrichment

Application a lot of mineral fertilizers has an unfavourable impact on our environment and health. All operation and method, which try to reduce the environmental pollutions have and will have a main role in our life. Environmental protection is getting more important for the agrarian, because of the purpose of sustainable agriculture (Pepo et al., 2005). Bio-fertilizers containing less mineral compounds and plant growth promoting bacteria are good tools to reduce environmental damages and enhance the yield (Levai et al, 2006). From the point of view the dry matter production, which is very important in agronomy, the photosynthetic efficiency and the dry matter production has a questionless role. Changes in the potential photochemical activity and the amount of dry matter are indicative for the adverse circumstances (Meszaros et al,. 2001, Veres et al., 2000).

Compensation effect of bacterium containing biofertilizer on the growth of Cucumis sativus L. under Al-stress conditions.

Several studies have demonstrated that selenium (Se) at low concentrations is beneficial, whereas high Se concentrations can induce toxicity. Controlling Se uptake, metabolism, translocation and accumulation in plants is important to decrease potential health risks and helping to select proper biofortification methods to improve the nutritional content of plant-based foods. The uptake and distribution of Se, changes in Se content, and effects of various concentrations of Se in two forms (sodium selenite and sodium selenate) on sunflower and maize plants were measured in nutrient solution experiments. Results revealed the Se content in shoots and roots of both sunflower and maize plants significantly increased as the Se level increased. In this study, the highest exposure concentrations (30 and 90 mg/L, respectively) caused toxicity in both sunflower and maize. While both Se forms damaged and inhibited plant growth, each behaved differently, as toxicity due to selenite was observed more than in the selenate treatments. Sunflower demonstrated a high Se accumulation capacity, with higher translocation of selenate from roots to shoots compared with selenite. Since in seleniferous soils, a high change in plants’ capability exists to uptake Se from these soils and also most of the cultivated crop plants have a bit tolerance to high Se levels, distinction of plants with different Se tolerance is important. This study has tried to discuss about it.

Contribution of Violaxanthin Cycle to the Stress Tolerance of Semiarid Grassland Species

Supplement of common fertilizers with selenium (Se) for crop production will be an effective way to produce selenium-rich food and feed. The value of green pea seeds and forages as alternative protein source can be improved by using agronomic biofortification. Therefore, biological changes of green pea (Pisum sativum L.) and influences of inorganic forms of Se (sodium selenite and sodium selenate) at different concentrations on the accumulation of magnesium (Mg) and phosphorus (P) were investigated in greenhouse experiment. 3 mg kg-1 of selenite had positive effects to enhance photosynthetic attributes and decrease lipid peroxidation significantly. At the same time, Se accumulation increased in all parts of plant by increasing Se supply. Moreover, Mg and P accumulations were significantly increased at 3 mg kg-1 selenite and 1 mg kg-1 selenate treatments, respectively. By contrast higher selenite concentrations (≥30 mg kg-1) exerted toxic effects on plants. Relative chlorophyll content, actual photochemical efficiency of PSII (ФPSII) and Mg accumulation showed significant decrease while membrane lipid peroxidation increased. Thus, the present findings prove Se biofortification has positive effects on biological traits of green pea to provide it as a proper functional product.