Date of Award:

5-1973

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Botany

Committee Chair(s)

Ivan Palmblad

Committee

Ivan Palmblad

Committee

Alvin Southard

Committee

Arthur Holmgren

Committee

Inge Dirmhirm

Abstract

Two species of the holartic genus Delphinium (D. occidentale S. Wats. and D. barbeyi Huth) were studied in the field and laboratory to determine the factors influencing the life stage development and distribution of these plants.

Delphinium occidentale, more widely distributed geographically and altitudinally than D. barbeyi, is found as a member of aspen and sagebrush communities. Sites are mesic in early spring but turn xeric by midsummer. Delphinium barbeyi, more limited in distribution geographically and altitudinally, appears to be limited to subalpine sites.

Adult biological properties are similar for both species. Morphological and taxonomic differences seem to be due to response to different community structure. Stem elongation of adult plants is initiated in late winter when buds on the caudex enlarge a few millimeters. Major growth does not occur until after snow melt. The stems terminate in racemes of dense, dark blue to purple flowers. Delphinium barbeyi plants are found with up to 55 individual stems. Maximum for D. occidentale is under 10.

The flowers produced are protandrous and pollinated by bumblebees. They are self-compatible and selfing probably does occur naturally when some stamens lag in anthesis. Fruits mature in late August or early September and seed is dispersed promptly. The great majority probably fall to the ground within a few centimeters of the plant when stalks are shaken by the wind.

Germination is epigeal and occurs under the snow from January on. Seedling growth under the snow is limited to root elongation.

Major differences between the species appear at the seedling stage. Thin, sessile cotyledons of D. occidentale persist in the field for up to 56 days. No true foliage leaves are formed during the first growth season. Onset of dormancy is brought on by maturation of the perennating bud and appears to be independent of the day length. Dormancy is initiated 7-10 days before available moisture in the top 15 cm of the soil becomes severely limiting. There is a possibility that the dormancy adaptation is an evolutionary response to the stresses encountered at this stage of the life cycle.

Delphinium barbeyi cotyledons are attached by separate petioles. The first foliage leaf appears 7-10 days after cotyledon appearance. Up to 4 leaves can develop during the first growth season. Dormancy does not occur until late August or early September.

Delphinium barbeyi appears to be the more robust plant. Reproductive maturity occurs during the fourth season of growth. By this age the root system is fully developed into the classic tap root form. Delphinium occidentale in contrast, only begins to develop a tap root system by the fourth year. It is possible that reproductive maturity does not occur in this species till 8-10 years of age.

Both species exist in nature as components of populations and are therefore subjected to the "strategies" of populations. As perennial plants Delphinium are repeating producers. They exhibit a long juvenile period of vegetative growth but once mature can possibly continue annual reproduction for up to 50 years. Data show high seed yield but low replacement among the adults.

It is possible that geographic and altitudinal distribution is controlled at the seedling and juvenile stages and not at the mature stage.

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