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Freezing tolerance is essential for perennial plants and ability to adapt to extreme temperature is crucial for their survival in many environments. Freezing tolerance of hardened and unhardened plants of Dactylis glomerata and Lolium perenne varieties was probed by their quantum photosynthetic efficiency using the chlorophyll fluorescence technique. Quantum yield of photosystem II (PSII) electron transport (Φ PSII ), maximal (F m ') and steady-state (F s ) chlorophyll fluorescence yields of light-adapted samples were measured. Φ PSII depended on developmental phase, temperature and hardening process. A clear decline in PSII activity, especially after -10°C application was observed. Plant hardening during emergence phase had a positive impact on PSII activity, especially after -5°C application. After 72 h of -5°C temperature treatment, hardened plants showed quicker recovery of their photosynthetic apparatus (0.527-0.697) as compared to unhardened ones (0.224-0.330). Stress temperature of -10°C caused irreversible changes of photosynthetic apparatus of hardened and unhardened plants independently of growth phases (0.003-0.014). Φ PSII and F m ' parameters were strongly correlated with shoots survival under stress. Our results suggest that perennial plants' hardening allows them to survive low temperatures due inter alia enhancing their photosynthetic machinery performance.

Plant dehydrin proteins (DHNs) are known to be important for environmental stress tolerance and are involved in various developmental processes. Two full-length cDNAs JcDHN-1 and JcDHN-2 encoding two dehydrins from Jatropha curcas seeds were identified and characterized. JcDHN-1 is 764 bp long and contains an open reading frame of 528 bp. The deduced JcDHN-1 protein has 175 a.a. residues that form a 19.3-kDa polypeptide with a predicted isoelectric point (pI) of 6.41. JcDHN-2 is 855 bp long and contains an open reading frame of 441 bp. The deduced JcDHN-2 protein has 156 a.a. residues that form a 17.1-kDa polypeptide with a predicted pI of 7.09. JcDHN-1 is classified as type Y₃SK₂ and JcDHN-2 is classified as type Y₂SK₂ according to the YSK shorthand for structural classification of dehydrins. Homology analysis indicates that both JcDHN-1 and JcDHN-2 share identity with DHNs of other plants. Analysis of the conserved domain revealed that JcDHN-2 has glycoside hydrolase GH20 super-family activity. Quantitative real time PCR analysis for JcDHN-1 and JcDHN-2 expression during seed development showed increasing gene expression of both their transcript levels along with the natural dehydration process during seed development. A sharp increase in JcDHN-2 transcript level occurred in response to water content dropping from 42% in mature seeds to 12% in dry seeds. These results indicate that both JcDHNs have the potential to play a role in cell protection during dehydration occurring naturally during jatropha orthodox seed development.

Abstract:Effective microorganisms impact on photosynthetic activity of Arabidopsis plant grown under salinity stress conditions. Salinity is one of the main abiotic stressors which affects plant growth through various physiological processes such as photosynthesis. The aim of this work is to study the impact of salinity stress on Arabidopsis plants by evaluating plant growth rate and photosynthetic activity, while investigating the influence of effective microorganisms (EMs) with the objective to determine if EMs could alleviate the induced stress affiliated with salinity. Results showed that salinity negatively affects photosynthesis efficiency in Arabidopsis plants based on the data obtained from the measured chlorophyll fluorescence parameters. Additionally, application of EMs enhanced plant tolerance to counteract the induced stress. Effective microorganisms concentration of 10 mL/L suggested to bring about the best results. This work advocates, that quantum efficiency of photosystem II (PSII) is a reliable indicator for tolerance in Arabidopsis plants to salinity stress, the impact of which may be softened by the EMs.

The optimization of cultivation process and improving the yield of perspective energy crops in Europe could be one of the ways to overcome the problem of limited amount of conventional fuel. The aim of this work was to check if the use of JIP-test, as a noninvasive method for early detection of the changes in photosynthetic apparatus, can be applied to detect nutrients deficiency in miscanthus (Miscanthus × gigantheus Anderss.) plants. The experiment was performed in fully randomized design with the following experimental variants: CaNPK (full fertilization, control), NPK (without calcium), CaKN (phosphorus poor), CaPK (nitrogen poor), CaPN (potassium poor), and Ca (without NPK). Our results revealed that the reaction of photosynthetic apparatus of miscanthus plants grown under certain macronutrient deficiency was associated with exclusive significant modifications in the measured chlorophyll fluorescence signals, analysed further by JIP-test. Analysis of chlorophyll fluorescence induction curves discovered substantial deficiency of phosphorus and potassium ahead of the standard chemical method.

This experimental work was undertaken to assess the effect of various fertilization regimes (CaNPK, NPK, CaPK, CaPN, CaKN and Ca) and different soil properties on growth and yield of Miscanthus plants and to check the impact of this plant on soil microbial characteristics. Field experiment was set up in 2003 on a long-term fertilization experiment, which had been established since 1923. Miscanthus giganteus response to high soil acidity and deficiency of N, P and K was investigated. Some physico-chemical and microbiological properties of soil samples were estimated and microbial characteristics of soil were conducted to investigate the number of the following microorganisms: heterotrophic bacteria, microscopic fungi, and some diazotrophic bacteria. Obtained results showed that, the highest yield of Miscanthus was obtained from the field fertilized with the CaNPK; while the lowest one was found for plants grown without nitrogen (CaPK). The high acidity of soil and small amount of phosphorus did not affect the yields in the NPK and CaKN combinations as compared with CaNPK one. The experiments showed that Miscanthus giganteus responded positively to mineral fertilization, especially with nitrogen. The rhizosphere of Miscanthus plants provides a suitable environment for the growth and development of microorganisms, in contrast to the non-rhizosphere zone.Keywords: energetic plant; microbial characteristics of soil; nutrients in plant and soil Plant Soil Environ. Vol. 60, 2014, No. 3: 117-122 118 MATERIAL AND METHODSThe object of chemical and microbiological analyses was soil taken under Miscanthus giganteus plants grown in different fertilization combinations. The experiment was set up in 2003 in triplicate on the site of a long-term fertilization experiment in which a fixed fertilization scheme had been applied since 1923: CaNPK, NPK, CaPK, CaPN, CaKN, Ca. The experiment was carried out on a podzolic soil formed from heavy loamy sand. Chemical and microbiological tests were carried out over 2010 and 2011 at three different times of the year (spring, summer, and autumn).Chemical tests were carried out on plants and non-rhizosphere soil, whereas microbiological tests included both rhizosphere and non-rhizosphere soils. Rhizosphere soil was taken to be the soil that remained within the root system of Miscanthus plants after shaking them.Soil samples were analysed for pH in 1 mol/L KCl (PN-ISO 10390), total nitrogen (PN-ISO 11261), organic carbon (PN-ISO 10694), available P by Egner-Riehm method (Fotyma et al. 2005), and exchangeable forms of K, Mg and Ca (Ostrowska et al. 1991). Plant samples were analysed for total amounts of macroelements (N, P, K, Mg, Ca, S) (Ostrowska et al. 1991).Microbial characteristics in the soil were assessed on the basis of population sizes of selected physiological groups of microorganisms: heterotrophic bacteria on the Bunt and Rovira medium (1955), and microscopic fungi on the Martin's medium (1950). The most probable number (MPN) of diazotrophic bacteria (Azotobacter sp. a...

Unfavourable growth conditions significantly determine the yield of crop plants. Intraspecific competition is a condition in which plants compete with each other for environmental resources. An excessive density contributes to increased competition within species, which results in disruption of photosynthesis process. According to this idea, experiments were conducted to investigate the photosynthetic response of potato (Solanum tuberosum) plants to excessive congestion. Two potato varieties of different earliness classes (Vineta and Satina) were used to evaluate the efficiency of the photosynthetic apparatus based on chlorophyll (Chl) fluorescence measurements under stress conditions. Changes in Chl contents of the tested plants were also analysed. In relation to intraspecific competition, we can conclude that the Vineta variety was less sensitive to this stress factor. In contrast, the photosynthetic apparatus of the Satina variety showed less efficient functioning under these conditions. In this study, the application of Chl fluorescence was presented for the first time in order to analyse the effects of intraspecific competition in plants.

The aim of this work was to determine two types of photosynthetic water-use efficiency in order to examine their utility as selection criteria for tolerance of energy crops to soil water deficit. Furthermore, effects of crop cultivation on soil water content and storage were investigated. Seven energy crops were examined: miscanthus, prairie cordgrass, willow, thornfree rose, Virginia mallow, Bohemian knotweed, and topinambour. The highest values of instantaneous (WUE) and intrinsic (WUE i ) water-use efficiencies were found for miscanthus and prairie cordgrass. The reduction of WUE and/or WUE i was caused mainly by a rapid rise in the transpiration rate and a greater stomatal conductance, respectively. Principal component analysis showed that neither WUE nor WUE i could be recommended as universal selection criteria for the drought tolerance in different energy crops. The proper localization of soil with a good supply of water is most the important condition for energy crop plantations.