MEASUREMENT OF THE SALINITY AND FREEZING TOLERANCE OF CRAT AEG US GENOTYPES USING CHLOROPHYLL

Abstract

The effect of increasing salinity and freezing stress singly and in combination on a range of chloro- phyll fluorescence parameters in foliar tissue of six Crataegus genotypes was examined. In general, increased stress reduced fluorescence values and absorption, trap- ping and electron transport energy fluxes per leaf reaction center and cross section, with decreased sigmoidicity of OJIP curves as a measure of the plastoquinone pool, reflecting decreased energy fluxes. Based on percentage reduction in a performance index from controls com- pared to stress-treate d values, plants were ranked in order of tolerant > intermediate > sensitive. Use of this Pip ranking criteria enabled the distinguishing of marked dif- ferences in foliar salt/freezing hardiness between the Crataegus species used. Interpretation of the photochemi- cal data showed that salinity and freezing affects both the acceptor and donor side of Photosystem II, while OJIP observations provided information regarding structural and functional changes in the leaf photosynthetic appa- ratus of the test species. It is concluded that chlorophyll fluorescence offers a rapid screening technique for as- sessing foliar salinity and freezing tolerance of woody perennials.