Arceuthobium pusillum: moisture requirements for germination and radicle growth

Abstract

Seeds of Arceuthobium pusillum were exposed to water, to various relative humidities, and to water followed weekly by various periods of dryness. With water, the seeds germinated more rapidly and produced longer radicles than with water in vapor form at any of the relative humidities used. At relative humidities between 90 and 100%, most of the seeds eventually germinated but the radicles remained short. Below 90% relative humidity, only a few seeds germinated. Some seeds germinated and produced radicles if exposed to weekly dry periods of up to 4 days.It is concluded that the distribution of the parasite is affected directly by water in liquid form, and indirectly by water in vapor form.