Comparing image (fractal analysis) and electrochemical (impedance spectroscopy and electrolyte leakage) techniques for the assessment of the freezing tolerance in olive

Abstract

Olive growth and productivity are limited by low temperatures mainly during winter, but sometimes also in spring and fall. The most effective way to avoid these damages in areas subjected to these climatic conditions is to select least susceptible varieties, but the choice of the right method to determine cold hardiness is extremely difficult. The aims of the work were (1) to assess LT50 (lethal temperature at which 50% of damage in plants subjected to low temperatures occurs) of some olive varieties in two seasons (summer and winter) and (2) to assess the reliability of different methods to evaluate cold hardiness. LT50 was determined on 21 different olive (Olea europaea L.) Italian varieties by leaf and shoot electrolyte leakage, shoot impedance spectroscopy and leaf color determination of fractal spectrum. All the experiments were conducted on non-acclimated and cold-acclimated plants. Our results showed that all the three methods were able to detect damages on olive plants after exposure to low temperatures, with leaves appearing more sensitive to cold stress than shoots. Among these methods, fractal analysis could be very useful in assessing cold hardiness of plants on the basis of visible injury, without sophisticated or expensive instruments and in a reliable and cost-effective way, using only a scanning device, a personal computer and dedicated freeware software.[...

Evidence for a role of raffinose in stabilizing photosystem II during freeze–thaw cycles

“…Likewise, the freezing injury was overestimated in conifer seedlings (Burr et al 1990), chaparral shrubs (Boorse et al 1998b) and various alpine species of the order Ericales (Yamori et al 2005). In contrast, the test yielded significantly lower LT 50 readings than impedance spectroscopy and fractal analysis in olive trees (Azzarello et al 2009). A possible explanation for these inconsistencies was given by Thomashow (1999), who pointed out that the EL test specifically reports the loss of semipermeability of the plasma membrane without necessarily detecting damage to other cellular structures.…”

Olive (Olea europaea L.) freezing tolerance related to antioxidant enzymes activity during cold acclimation and non acclimation

“…Previous studies also showed that there is a correlation between some physiological and biochemical characteristics such as stomatal density (Roselli et al 1989), stomatal size (Roselli and Venora 1990), phenolic compounds (Roselli et al 1992), differential thermal analysis (Martin et al 1993), ionic leakage Azzarello et al 2009), fractal analysis (Azzarello et al 2009), impedance spectroscopy (Azzarello et al 2009), soluble sugars Bartolozzi et al 2001;Gulen et al 2009) and total soluble proteins (Eris et al 2007;Cansev et al 2009) with frost-tolerant in olive genotypes. Currently, interesting results to quantify cold tolerance have come from the study of some antioxidant enzymes (Solecka and Kacperska 2003;Cansev et al 2009;Ortega-García and Peragón 2009).…”

Antioxidant changes of Thomson navel orange (Citrus sinensis) on three rootstocks under low temperature stress

“…It is also known that the formation of ROS enhances peroxidation at the cellular level that is related to plant genotype and the severity of stress (Navari-Izzo et al , 1996). Variations in MDA contents were found in coffee (Campos et al, 2003) and olive plants (Azzarello et al, 2009) cultivars at low temperature stress. Our research found significantly increased MDA contents in Thomson navel orange under low temperature stress.…”

“…Low temperature stress induced an increase in lipid peroxidation in coffee (Campos et al, 2003) and olive plants (Azzarello et al, 2009). Fotouhi et al (2008) reported four to seven times electrolyte leakage greater than those in control plants in freezing stressed Mexican lime seedlings.…”