No abstract

The application of chlorophyll fluorescence measurements to screening barley (Hordeum vulgare 1.) genotypes for salinity tolerance has been investigated. Excised barley leaves were cut under water and incubated with the cut end immersed in water or in a 100-mM NaCl solution, either in the dark or in high light. Changes in rapid fluorescence kinetics occurred in excised barley leaves exposed to the saline solution only when the incubation was carried out in the presence of high light. Fluorescence changes consisted of decreases in the variable to maximum fluorescence ratio and in increases in the relative proportion of variable fluorescence leading to point I in the Kautsky fluorescence induction curve. These relative increases in fluorescence at point I appeared to arise from a delayed plastoquinone reoxidation in the dark, since they disappeared after short, far-red illumination, which is known to excite photosystem I preferentially. We show that a significant correlation existed between some fluorescence parameters, measured after a combined salt and high-light treatment, and other independent measurements of salinity tolerance. These results suggest that chlorophyll fluorescence, and especially the relative fluorescence at point I in the Kautsky fluorescence induction curve, could be used for the screening of barley genotypes for salinity tolerance.

Effects of combined NaCl and CaCl, salinity on photosynthetic parameters of barley grown in nutrient wjlution. -Physiol. Plant. 86: 419-426,The changes caused by NaCl-and CaCli-induced salinity on several leaf parameters have been measured in two cultivars of barley {Hordeum vulgare L.) growing in a growth chamber in nutrient solution. Salinity was induced by adding to the nutrient solution equal weights of NaCl and CaCl,, to obtain conductivities of 2, 6, 12, 19 and 26 dS m ^ Salinity induced decreases in the leaf water potential and in the osmotic potential. Salinity did not induce significant changes in the relative photosynthetic pigment composition of barley leaves, the photosynthetic pigment stoichiometry tor neoxanthin:violaxanthin cycle pigments:lutein:/9-carotene:Chl 6:Chl a being close to 3:6:14:12:25:100 (mol:mol). Sahnity per se did not induce interconversions in the carotenoids within the violaxanthin cycle in most barley leaves. The PSIl photochemistry of most barley leaves was unchanged by salinity. However, some apparentlyhealthy leaves growing in high salinity exhibited sudden decreases in PSII photochemistry and increases in zeaxanthin (at the expense of violaxanthin), that preceded rapid leaf drying. Salinity induced significant changes in the slow part of the chlorophyll fluorescence induction curve from barley leaves.

Waterlogging is associated with poor soil drainage. As a consequence oxygen levels decrease in the root environment inducing root asphyxia and affecting plant growth. Some plants can survive under these conditions triggering complex anatomical and biochemical adaptations, mostly in the roots. Long- and short-term responses to waterlogging stress were compared in two trials using a set of two myrobalans (Prunus cerasifera Erhr), 'P.2175' and 'P.2980', as tolerant rootstocks and two almond × peach [Prunus amygdalus Batsch ×Prunus persica (L.) Batsch] interspecific hybrids, 'Garnem' and 'Felinem', as sensitive ones in two consecutive years. Stomatal conductance and chlorophyll content were measured in the long-term trials to assess survival performance, while the enzyme activities of superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (POD, EC 1.11.1.7), and catalase (CAT, EC 1.11.1.6) were measured in the short-term trials to study early antioxidant response. The incidence of the stress in the root environment was different as a result of the different plant development at the moment of the treatment, as a consequence of different environmental conditions both before and during the treatment between the 2 years. The activity of the different enzymes was higher in the sensitive genotype 'Felinem' than in the tolerant 'P.2175'. This result shows an activation of the antioxidant system and has been observed to depend of the different nature of the roots between the 2 years. As the antioxidant enzymes seem to work more efficiently when roots are more aerated, we cannot conclude that they are responsible for the higher tolerance observed in the myrobalan plums.