Marian Brestic

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.

Involvement of Chlorophyll a Fluorescence Analyses for Identification of Sensitiveness of the Photosynthetic Apparatus to High Temperature in Selected Wheat Genotypes

The aim of our work was to evaluate the sensitivity of testing procedure and different parameters derived from the basic parameters of chlorophyll a fluorescence as well as from fluorescence kinetics analysis for their application in screening of wheat genotypes. In several testing cycles during vegetation period we examined a set of 31 wheat (Triticum aestivum L.) genotypes and local landraces of different provenances cultivated in the field trials of the RICP Piestany, Slovak Republic. In all tests we used procedure of heating of detached leaf segments closed in glass tubes for 1 hour immersed in the thermostated water bath (40 °C) in the dark. Before and after the heat treatment, the chlorophyll a fluorescence in a fast phase was used. To compare the leaf samples we used the maximum quantum yield of PSII photochemistry FV/FM and, relative variable fluorescence at 0.3 ms (WK). The results showed considerable differences in heat sensitivity among wheat genotypes, and offered a potential to identify more tolerant or susceptible genotypes. The termostability increased and genotypic differences decreased across the vegetation period. Parameter derived from the fluorescence kinetics (Wk) was generally more sensitive and hence more useful than the basic chlorophyll fluorescence parameter (FV/FM).

Critical Temperature Derived from the Selected Chlorophyll a Fluorescence Parameters of Indigenous Vegetable Species of South Africa Treated with High Temperature

In our experiments we aimed at testing of photosynthetic thermostability using chlorophyll fluorescence measurements in non-stressed and in drought-stressed conditions. All measurements were realized at 6 species (Vigna unguiculata, Corchorus olitorius, Cucurbita pepo, Amaranthus sp., Brassica rapa, and Hordeum vulgare as a reference). Plants were grown in pots in climatized growth chamber in moderate conditions. The main practice was temperature test with the chlorophyll fluorescence measurements realized after exposure at 38 °C to 50 °C in circulation water bath. We determined critical temperature values for basal fluorescence — F0 increase, maximum quantum yield of photochemistry Fv/Fm and we identified also temperature inducing K-step appearance in rapid fluorescence kinetic indicating impairment of oxygen evolving complex (OEC). Our results show significant differences among species in critical temperature. As the most susceptible species was found Brassica and Amaranthus substantially affected by temperatures about 40 °C with almost negligible increase of critical temperature in drought-stressed conditions, moderate susceptibility in Barley with increase of thermostability caused by moderate drought and high heat tolerance in Cucurbita, Vigna and Corchorus. If we focus on individual florescence parameters used for testing, the K-steps appeared at temperature 1–2 °C higher than initial Fv/Fm decrease, the antennae deconnection indicated by F0 increase appeared generally at 3–4 °C higher temperature, in some cases was not evident even at 50 °C.

Noninvasive Methods to Support Metabolomic Studies Targeted at Plant Phenolics for Food and Medicinal Use

Metabolomics has emerged as an important tool in many disciplines, including research of plant resources for food and pharmaceutical use. Despite the development of modern, high-throughput methods, the analyses are still relatively costly and laborious. In this chapter, we present the noninvasive fluorescence-based methods, typically used in plant phenomics, which may serve as early steps in metabolomic screening targeted at nutritionally and pharmaceutically important phenolic compounds. The presented results of in situ measurements in a high number of plant species indicate a high interspecific variability, which seems to be promising for further studies. The principle of the methods, previous applications as well as future possibilities are dealt with.

The Involvement of Different Secondary Metabolites in Salinity Tolerance of Crops

Salt stress decreased plant growth and development; affects carbon metabolism, ion toxicity, nutritional status, and oxidative metabolism; and modulates the levels of secondary metabolites which are important physiological parameters in salt stress tolerance. Recent progress has been made in the identification and characterization of the mechanisms that allow plants to tolerate high salt concentrations and drought stress. Accumulation of secondary metabolites often occurs in plants subjected to stresses including various elicitors or signal molecules. The focus of the present chapter is the influence of salt stress on secondary metabolite production and some of important plant pharmaceuticals. Enhanced synthesis in the cytosol of determined secondary metabolites (anthocyanins, flavones, phenolics, and specific phenolic acids) under stress condition may protect cells from ion-induced oxidative damage by binding the ions and thereby showing reduced toxicity on cytoplasmic structures. The aim of this study was to determine the physiological implication of secondary metabolites in salt-tolerant crops.

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.