The use of nondestructive methods to assess a physiological status and conservation perspectives of Eryngium maritimum L.

Eryngium maritimum is a perennial species growing exclusively in a coastal littoral zone both on sand dunes and shingle beach and indicated as declining in Northern Europe. The objective of the present study was to prove the use of nondestructive physiological measurement methods to access physiological status of endangered plants, using E. maritimum as a model species. Plants from two Latvian sites were studied in comparison with other populations in Northern Europe (Estonia, Lithuania, Poland, United Kingdom) to find out if local differences in environmental factors affect vitality of E. maritimum individuals. Noninvasive chlorophyll analysis and chlorophyll a fluorescence measurements were used as indicators of plant physiological status through characterization of various aspects of photochemistry of photosystem II activity. Dynamics and morphology of individuals were investigated for evaluation of clonal growth potential of E. maritimum in natural conditions. Highly fluctuating trend of dynamics of individuals (within 40 groups at two Latvian sites) was established for E. maritimum in natural conditions over a five-year period. Disturbance of individuals lead to formation of new shoots from nodal root meristems. An exponential regression between fluorescence parameters F_V/F_M and Performance Index and summary monthly precipitation was found indicating that E. maritimum plants had significant tolerance to water shortage together with susceptibility to increased precipitation. Negative correlation between leaf chlorophyll content and more northern localization of individuals was found (r = 0.95 and r = 0.94, for generative and vegetative shoots, respectively). Northern populations of E. maritimum are endangered by high precipitation in conditions of low air temperature, leading to decrease of photosynthetic productivity and overall physiological status. High developmental plasticity at the root level leads to clonal growth and an efficient survival and relatively long life span of E. maritimum individuals. Chlorophyll a fluorescence is a useful method to search for the effect of suboptimal conditions on physiological status of endangered plant species without elimination and disturbance of individuals.