THE AMINO ACIDS OF SOME MISTLETOES AND THEIR HOSTS

The following mistletoes and their hosts were studied: Phoradendron serotinum (Raf.) M. C. Johnst. (P. flavescens [Pursh] Nutt. var. macrophyllum Engelm.) on Juglans hindsii Jeps. (California black walnut), Arceuthobium campylopodum Engelmn. f. abietinum (Engelm.) Gill on Abies concolor (Gord. and Glend.) Lindl. (white fir) and A. magnifica A. Murr (red fir), Arceuthobium campylopodum Engelm. f. campylopodum (Engelm.) Gill on Pinus sabiniana Dougl. (Digger pine), and Amyema pendula (Spleng) Tiegh. on Eucalyptus macrorhyncha F. Muell. ex Benth. (stringybark). With the exception of the Amyema leaves, the mistletoes are richer in free and bound amino acids than their hosts; moreover, their amino acid composition closely resembles that of their hosts. Nevertheless, there is no satisfactory evidence that mistletoe specificity depends on the amino acid composition of the hosts. Some mistletoes contain γ-aminobutyric acid and asparagine, not found in all hosts. All the above mistletoes but no hosts contain free hydroxyproline. These results are discussed in relation to (1) the region in the mistletoes where hydroxyproline is formed and (2) the possibility of using certain amino acid analogs as selective poisons for mistletoes.