Seed weight and germination time affect growth of 2 shrubs.

Abstract

The objective of this study was to investigate relationships between seed size, time of germination, and seedling growth in winterfat (Ceratoides lanata (Pursh) J. T. Howell) and silver sagebrush (Artemisia cana Pursh). Individual seeds of winterfat were placed into 6 weight classes ranging from 1.5-2.0 to > 4.0 mg seed-1 while silver sagebrush seeds were separated into 7 classes ranging from 0.53 to 0.83 mg seed-1. Seeds were incubated at 18 degree C, seedlings with radicles < 3.0 mm were removed at 1, 2, 3, 4-5 and 6-12 day intervals, grown 5 days in darkness at 18 degree C, and axial length measured. Total germination of winterfat increased 5.5% mg-1 increase in seed weight, but germination rate was similar among weight classes, averaging 53.1% day-1. Seed weight and time of germination interactively influenced growth of winterfat seedlings. Seedling length of winterfat was more than 2-fold greater in the > 4.0 than the 1.5-2.0 mg seed-1 class while lengths of seedlings in the > 2.0-2.5 through > 3.5 to 4.0 mg seed-1 weight classes were intermediate. Seedling length decreased 0.9 to 3.3 mm for each day that germination was delayed from 1 to 12 days with the least and greatest inductions occurring for lightest and medium weight seeds, respectively. Total germination for silver sagebrush initially increased with seed weight, but declined at weights greater than about 0.57 mg seed-1; germination rate was similar (57.1% day-1) among weight classes. Seedling length of silver sagebrush increased 0.3 mm mg-1 increase in seed weight whereas length decreased curvilinearly as time to germination was delayed. When winterfat is used for restoration, relatively heavy seeds should be used because they have the greatest germination and produce large seedlings. Because seedling length of silver sagebrush increased with increasing seed weight it is also desirable to select heavier seeds; however, reduced germination in heavier seeds may necessitate increasing seeding rates.