Hazem M. Kalaji

Impact of Metal and Metal Oxide Nanoparticles on Plant: A Critical Review

An increasing need of nanotechnology in various industries may cause a huge environment dispersion of nanoparticles in coming years. A concern about nanoparticles interaction with flora and fauna is raised due to a growing load of it in the environment. In recent years, several investigators have shown impact of nanoparticles on plant growth and their accumulation in food source. This review examines the research performed in the last decade to show how metal and metal oxide nanoparticles are influencing the plant metabolism. We addressed here, the impact of nanoparticle on plant in relation to its size, concentration, and exposure methodology. Based on the available reports, we proposed oxidative burst as a general mechanism through which the toxic effects of nanoparticles are spread in plants. This review summarizes the current understanding and the future possibilities of plant-nanoparticle research.

Chapter 15 – The Use of Chlorophyll Fluorescence Kinetics Analysis to Study the Performance of Photosynthetic Machinery in Plants

Plants under natural conditions experience unfavorable growth conditions. These can cause a reduction of their photosynthetic rate or even damage the photosynthetic apparatus, which can lead to a serious decrease of plant productivity and yield. Photosynthesis is sensitive to environmental limitations, which means that photosynthetic measurement is an important tool for plant stress studies. Nevertheless, classic methods, such as the measurement of photosynthetic rates through gas exchange (CO2, H2O, and O2), are time-consuming and give incomplete information about photosynthetic function. Thus, the introduction of methods based on chlorophyll a fluorescence has led to a significant breakthrough in photosynthesis research. In this chapter we discuss the wide range of chlorophyll a fluorescence applications to understand the response of the photosynthetic apparatus to various stress conditions. We concentrate on demonstrating the so-called “OJIP test” as a good tool to explore the response of photosystem II (PSII). In addition, we discuss the issue of PSII heterogeneity under unfavorable growth conditions.

Heat Signaling and Stress Responses in Photosynthesis

High temperature represents one of the most serious abiotic stress factors limiting plant photosynthesis, biomass production, and crop productivity. Photosynthetic apparatus is an important heat sensor in plants, sensing a wide range of air temperatures, from moderate to extreme. In this chapter we offer current knowledge on both photochemical and metabolic changes occurring within the photosynthetic apparatus in conditions of heat stress associated with signaling and stress response. The heat stress directly affects the heat-sensitive sites, mainly oxygen-evolving complex of photosystem II and Rubisco activase. It leads to subsequent indirect effects, such as changes of the redox status of individual components on thylakoid membrane in chloroplast and increase in production of reactive oxygen species (ROS). Hence, the redox signaling plays the crucial role in enhancement of alternative electron pathways such as cyclic electron flow as well as triggering the signal transduction pathways resulting to heat-stress response. The redox signaling in chloroplast is closely associated with ROS signaling, which interferes with regulation also out of chloroplast. The stress response involves mainly production of specific proteins (mostly heat shock proteins or antioxidants) or protective compounds (osmoprotectants) leading to increase of thermostability of sensitive sites or protection against ROS. Different signal molecules contribute in photosynthesis-related heat-stress signaling pathways, such as reactive oxygen species with hydrogen peroxide, nitric oxide, calcium, and abscisic acid. The specific roles of cytokinins and isoprene in heat-stress response are also reviewed.

Regulation and physiological role of silicon in alleviating drought stress of mango

Improvement of drought stress of mango plants requires intensive research that focuses on physiological processes. In three successive seasons (2014, 2015and 2016) field experiments with four different strains of mango were subjected to two water regimes. The growth and physiological parameters of possible relevance for drought stress tolerances in mango were investigated. Yield and its components were also evaluated. The data showed that all growth and physiological parameters were increased under K2SiO3 (Si) supplement and were followed by the interaction treatment (Si treatment and its combination with drought stress) compared to that of the controlled condition. Drought stress decreased the concentration of auxins (IAA), gibberellins (GA) and cytokinins (CK) in the three mango cultivars leaves, whereas, it increased the concentration of abscisic acid (ABA). On the contrary, IAA, GA, and CK (promoters) endogenous levels were improved by supplementing Si, in contrary ABA was decreased. Drought stress increased the activity of peroxidase (POX), catalase (CAT), and superoxide dismutase (SOD) in the leaves of all mango cultivars grown during three experimental seasons. However, Si supplementation reduced the levels of all these antioxidative enzymes, especially the concentration of SOD when compared to that of control leaves. Fruit quality was improved in three successive seasons when Si was applied. Our results clearly show that the increment in drought tolerance was associated with an increase in antioxidative enzyme activity, allowing mango plants to cope better with drought stress. Si possesses an efficient system for scavenging reactive oxygen species, which protects the plant against destructive oxidative reactions, thereby improving the ability of the mango trees to withstand environmental stress in arid regions.

Development of insect resistant maize plants expressing a chitinase gene from the cotton leaf worm, Spodoptera littoralis.

Due to the importance of chitinolytic enzymes for insect, nematode and fungal growth, they are receiving attention concerning their development as biopesticides or chemical defense proteins in transgenic plants and as microbial biocontrol agents. Targeting chitin associated with the extracellular matrices or cell wall by insect chitinases may be an effective approach for controlling pest insects and pathogenic fungi. The ability of chitinases to attack and digest chitin in the peritrophic matrix or exoskeleton raises the possibility to use them as insect control method. In this study, an insect chitinase cDNA from cotton leaf worm (Spodoptera littoralis) has been synthesized. Transgenic maize plant system was used to improve its tolerance against insects. Insect chitinase transcripts and proteins were expressed in transgenic maize plants. The functional integrity and expression of chitinase in progenies of the transgenic plants were confirmed by insect bioassays. The bioassays using transgenic corn plants against corn borer (Sesamia cretica) revealed that ~50% of the insects reared on transgenic corn plants died, suggesting that transgenic maize plants have enhanced resistance against S. cretica.

The application of potato starch effluent causes a reduction in the photosynthetic efficiency and growth of Scots pine (Pinus sylvestris L.)

Key messageThe high concentration of N and K caused a weakening of physiological conditions of the trees. Application of N, P and K from starch effluent is not a suitable method of waste management.AbstractSince 1984, potato starch effluent has been applied to trees in the Iława Forest Inspectorate to promote the biological utilization of this waste product containing high amounts of nitrogen (N), phosphorus (P) and potassium (K). We examined the tree rings of Scots pine (Pinus sylvestris L.) to study the effect of intensive fertilization on tree rings. A total of 120 samples were taken from three sites representing a fertilized and unfertilized area and trees growing at a control site, outside the forest waste water system. We found that February and March temperature influenced the growth of tree rings. We used multiple regression to investigate the influence of N, P and K concentration, the amount of waste water and February and March temperature upon tree growth. Akaike information criterion (AIC) model selection was applied to choose the most influential factors upon growth, and additional multiple regression analyses were performed for two subsets of variables. Trees growing on the unfertilized site responded positively to N content and negatively to P content. For the fertilized site, the high concentration of N and K together with decreasing volume of waste water caused a growth decline. Trees from fertilized area also showed a decrease in their photosynthetic efficiency.

Biophysical Phenotyping as an Essential Tool for Understanding Host–Microbe Interaction

The symbiotic relationship between plant and microbes is one of the most important types of symbiosis among different living forms. Such kind of association helps both the host and the symbiont. Generally, bacteria and fungi are found in association with a variety of plants. It is believed that more than 80 % of plants from different families available on the earth surface have a symbiotic association with arbuscular mycorrhizal fungi. In this context, it is very important to understand the host–microbe interaction, which will elucidate the exact mechanisms involved in the symbiosis.

The influence of phosphite treatments on oak leaves and damage caused by powdery mildew Erysiphe alphitoides

Abstract The aim of the project was to check the influence of ammonium phosphite preparation − Actifos on the physiology of leaves and a possible reduction of infection by the fungus a year after the application of fertilizer. Three observation plots were selected in Karczma Borowa, Krotoszyn and Piaski Forest Districts (FD). In each of these observation plots, trees were chosen randomly. In Karczma Borowa FD, the trees were treated by watering them with a 3% solution of Actifos. In Krotoszyn FD, the leaves of trees were sprayed twice (in July and September) from the plane using a 50% solution of Actifos; and in Piaski FD, only the trunks of tress were sprayed twice the same way, but in July 2012 and September 2013. In October 2013, from each tested tree, ten leaves were selected randomly from the upper, well-lit parts of their crowns. The assessment of leaf surface damaged by mycelium and chlorophyll a fluorescence was performed. After the application of the phosphite, no negative physiological consequences for the treated trees were noticed − neither concerning the average leaf area nor the fluorescence of chlorophyll. The manner of phosphite application (leaves, trunks or roots) did not cause any negative consequences for the vitality/health of the treated trees as compared to the control trees. A certain tendency in the reduction of oak mildew on the treated leaves with phosphite was observed, however these observations should be continued in the next years.