Andreas Karamanos

Organic Maize Growth and Mycorrhizal Root Colonization Response to Tillage and Organic Fertilization

The influence of conventional and no-tillage on mycorrhizal root colonization, soil properties and yield, was studied for 2 years in an experimental field of organic maize, fertilized by cattle manure or by seaweed compost. The no-tillage system improved soil macroporosity, increased organic carbon content, and enhanced the mean weight diameter of soil aggregates. Similarly, it had a positive effect on plant growth. Root density, leaf area index, biomass, grain yield and mycorrhizal root colonization were significantly affected by tillage system. Fertilization with manure and compost improved soil structure and aeration, thus favoring a higher mycorrhizal colonization of organic maize. The improved soil physical properties were positively related to mycorrhizal root colonization. High correlation coefficients of determination (r2) were also found between mycorrhizal root colonization and plant characteristics. It is concluded that the no-tillage system can improve the productivity of organic agriculture via pronounced arbuscular mycorrhizal root colonization.

Modification of water entry (xylem vessels) and water exit (stomata) orchestrates long term drought acclimation of wheat leaves

Immediate leaf functional responses to drought, such as stomatal closure and photosynthetic rate reduction, are already known from short-term studies. We tested the hypothesis that long-term acclimation of leaves to drought includes hydraulic and stomatal anatomical changes and that gas exchange and nitrogen allocation patterns are inevitably adjusted to the new structural status. 26 structural and functional traits in one sensitive cultivar (Simeto) and two drought resistant landraces (Ntopia Heraklion 184, Kontopouli 17) of field- grown wheat (Triticum turgidum L. var. durum) were examined under four water shortage levels. Drought acclimation responses were more intense in Simeto than in the two landraces. In accordance to the working hypothesis, drought-acclimated leaves showed lower hydraulic conductance due to narrower vessels and higher stomatal and vein densities than the control leaves, resulting in a safe mode of water transfer and consumption which is essential for the survival in water limiting conditions.Irrespectively of genotype and water regime, significant correlations among structural (hydraulic characteristics, stomatal and vein patterns) and functional (gas exchange, nitrogen content) parameters were found, indicating the functional adjustment to the new structural status. The Principal Component Analysis showed that these structure-function interactions reflected the trade-off between growth and protection against water losses (Axis 1), as well as the competition between different sinks (carbon gain vs structural reinforcement and reproductive effort) in N allocation (Axis 2). Drought acclimation in wheat leaf is integrally processed by the coordination of structural and functional parameters in order to compensate for the adverse effects of water shortage. This structure—function network that regulates the transition from normal growth-mode to protection- mode, includes at least two important “nodal points”: xylem conducting efficiency (water entry) and stomatal function (water exit). This transition also includes the redirection of nitrogen resources to different sinks.

Determination of Isoflavones in the Aerial Part of Red Clover by HPLC-Diode Array Detection

Abstract Red clover (Trifolium pratense L.) is a biennial plant which has been used as feeding material for ruminants, but also as a health food for humans due to its estrogenic, antispasmodic, and expectorant properties. Red clover contains a large number of flavones, the four most important being daidzein and genistein and their precursors formononetin and biochanin A, respectively. The purpose of the current project was to quantify these four isoflavones in the aerial part of red clover in samples collected at the flowering, vegetative, and fruiting stages, and accordingly, to determine which of the three growth stages of red clover, contains the highest isoflavone amount. Thus a method based on reversed‐phase high performance liquid chromatography (HPLC) using diode array detection has been developed and validated. The linearity, precision, accuracy, and sensitivity of the method allow for the fast and reliable determination of the aforementioned substances from the aerial part of red clover. Analysis of the plant at different growth stages showed that the highest amount of isoflavones was detected during the vegetative stage.