Photosynthetic rates in relation to nitrogen recycling as an adaptation to nutrient deficiency in peat bog plants

Abstract

Fifteen species growing in a raised sphagnum peat bog were compared with 13 non-bog species with respect to their light-saturated net photosynthetic rate, and the content of N, P, and K within their foliage and leaf litter. Bog species were found to reabsorb significantly more nitrogen from their foliage preceding leaf fall than non-bog species. An estimate of the potential photosynthate which the species could manufacture during the time a given unit of nitrogen remained in the plant, before being lost through leaf fall, was calculated for the 28 species. The values found averaged 235% higher for the bog evergreens than for the bog deciduous species, and about 60% higher in the bog deciduous species than in the non-bog deciduous species. The hypothesis is advanced that the increased time available to use nitrogen photosynthetically before it is recycled is adaptive in bog plants, especially in evergreens, because of the difficulty in acquiring nitrogen from the extremely nutrient-deficient bog substrate.