Eco-physiology of Primula farinosa Linn, and some allied species
Ecological and physiological comparisons were made mainly between two populations of Primula farinosa Linn, from northern England and some of their closely related arctic-alpine species:- P. frondosa, P. darialica, P. halleri, P. laurentiana, P. modesta, P. scotica, P. scandinavica, and P. stricta, which have contrasting habitats and natural distribution. The germination of primulas showed a negative or neutral response to the density of seeds sown. They also showed intrinsic seed-dormancy which can be overcome by chilling treatment. Most of the species tested had significantly higher percentage germination in a diurnally fluctuating temperature regime than at 15ºC constant temperature. The results from analyses of leaf characteristics showed significant variation between species studied. Significant correlations were found between chromosome numbers of the species studied and some leaf characteristics, e.g. cell size, stomatal index. Plant growth analyses were investigated along an altitudmal gradient in the north of England. Both vegetative and reproductive growth was clearly affected by microclimate. The primulas showed more sensitive responses to drought than frost as regards to their survival. They responded to water stress by accumulating proline as well as increasing their total protein contents. Photosynthesis measurements showed optimum temperature for O(_2) evolution at warm temperatures of 20-25ºC. The difference in physiological performances of the primulas is discussed in relation to their leaf characteristics, ploidy levels and habitats of origin. This study demonstrates clearly that the two populations of P. farinosa differed in a number of morphological and physiological characteristics; some of which could make it possible for the different races to occupy different ecological habitats.