Nitrogen Nutrition of the Tuberous Sundew Drosera erythrorhiza Lindl. With Special Reference to Catch of Arthropod Fauna by Its Glandular Leaves

Abstract

The feedlng of 15N labelled Drosophila fles to leaf rosettes of Drosera erythrorhiza Llndl resulted in the enrichment of leaves, stems and daughter and replacement tubers with 15N. A transfer of 76% of the labelled nitrogen from the insects to the Drosera was recorded, and by the end of the growing season the new set of tubers had acqulred 70% of the applled 15N The 15N was traced through two subsequent seasons of growth in order to study the extent of carryover of insect-derived nltrogen between successive generations of tubers Seasonal changes in nltrogen of D erythrorhlza in natural habltat bore evldence of a hlgh degree of transfer of nitrogen from tubers to vegetative parts and vice versa. Tubers had 50-60% of their nltrogen in soluble form, principally as arginine. Stems and leaf rosettes had lower proportions of soluble nitrogen and less arginine. Arginine of the tubers became labelled with 15N after feeding 15N-labelled Drosophila Arthropods caught by naturally growlng clones of D erythrorhiza included Collembola, Diptera, Hymenoptera, Hemlptera, Coleoptera and Arachnids Assuming there was a 76% transfer of nltrogen from fauna to Drosera, the season's catch of from 0.25 to 0.39 mg nitrogen per plant provlded the equivalent of from 14 to 21% of the nltrogen transferred to the new season's tubers and from 11 to 17% of the plant's net uptake of nitrogen durlng a growlng season Phenotypic varlants lacklng glandular tentacles occurred sporadically in natural and pot-grown populations of D erythrorhlza Plants lackmg tentacles proved incapable of absorbing the 14C of 14C-labelled insects They reverted to the production of a full or partlal complement of tentacles In a subsequent season of grouth