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