One-Year Ponderosa Pine Seedling Produces Pollen

Abstract

A greenhouse-grown Pinus ponderosa var. scopulorum produced pollen at the early age of 1 year. Stress is hypothesized as the cause of the precocious cone-production. Pollen viabil- ity tests were negative. Minimum age of staminate cone production in Pinus ponderosa var. sco- pulorum Engelm. (Rocky Mountain ponderosa pine) has not previously been ascertained. Generally, onset of reproductive maturity does not occur until an age of 6 to 20 years. However, Righter (1939) found that ovulate cones may be produced as early as 5 years, but did not report a minimum age for staminate cone development. Staminate cones were found by Righter (1939) on P. ponderosa var. ponderosa Laws. (typical ponderosa pine) at 2 years. Because Rocky Mountain ponderosa pine currently is the object of tree improvement research, reduction in breeding cycle length is of great practical importance. Production of precocious cone-bearing trees is a means of shortening the generation time. Stress has been shown to induce precocious cone-production (Pharis, 1977; Quirk, 1973; Sweet and Will, 1965) and as such was employed in this study.