The Ecological Life Cycle of the Cedar Glade Endemic Lobelia gattingeri

Jerry M. Baskin; Carol C. Baskin

doi:10.2307/2484550

The ecological life cycle of the cedar glade endemic Leavenworthia exigua var. exigua

Canadian Journal of Botany ◽

10.1139/b72-212 ◽

1972 ◽

Vol 50 (8) ◽

pp. 1711-1723 ◽

Cited By ~ 6

Author(s):

Jerry M. Baskin ◽

Carol C. Baskin

Keyword(s):

Life Cycle ◽

Winter Season ◽

Rest Period ◽

Early Spring ◽

Flower Bud ◽

Early Autumn ◽

Wide Range ◽

Cedar Glade ◽

Maximum Temperatures ◽

Subsequent Flowering

Field, laboratory, and greenhouse studies were conducted on the ecological life cycle of the cedar glade endemic Leavenworthia exigua var. exigua over a 2-year period. Leavenworthia exigua var. exigua completes its life cycle (seed to seed) during autumn, winter, and early spring and is in the dormant seed stage from midspring to early autumn. This winter annual type of life cycle strategy is an adaptation of the species to its summer-arid, winter-wet habitat.Seeds of L. exigua var. exigua exhibit true dormancy at maturity and dispersal in spring. The seeds gradually afterripen during the spring–summer rest period. During the afterripening period the seeds pass from true (innate) dormancy to relative (conditional) dormancy then to a state of non-dormancy. After entering relative dormancy the temperature range for germination is widened through an increase of the maximum temperatures over which germination can occur. By early autumn most of the seeds in a population are completely non-dormant and can germinate over a wide range of temperatures, including those that normally occur in early autumn in its habitat. The exact time of germination in autumn is controlled by soil moisture. This type of afterripening pattern and germination control is an adaptation of the species to a hot, dry season.Although flower buds are formed during late autumn and early winter, the low temperatures and short photoperiods that accompany the winter season are not required for flower bud initiation and subsequent flowering. The main effect of low winter temperature on L. exigua var. exigua is that it slows growth and development and thus delays flowering and fruiting until early spring.

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Ultrastructural analysis of “Sensory” surface nerve endings and “putative” neurotransmitter sites in Schistosoma mansoni Miracidia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156791 ◽

1989 ◽

Vol 47 ◽

pp. 962-963

Author(s):

Betty Ruth Jones ◽

Steve Chi-Tang Pan

Keyword(s):

Nervous System ◽

Life Cycle ◽

Schistosoma Mansoni ◽

Snail Host ◽

Complex Life Cycle ◽

Rational Approach ◽

Effective Control ◽

The Social ◽

Social And Economic Development ◽

Basic Biology

INTRODUCTION: Schistosomiasis has been described as “one of the most devastating diseases of mankind, second only to malaria in its deleterious effects on the social and economic development of populations in many warm areas of the world.” The disease is worldwide and is probably spreading faster and becoming more intense than the overall research efforts designed to provide the basis for countering it. Moreover, there are indications that the development of water resources and the demands for increasing cultivation and food in developing countries may prevent adequate control of the disease and thus the number of infections are increasing.Our knowledge of the basic biology of the parasites causing the disease is far from adequate. Such knowledge is essential if we are to develop a rational approach to the effective control of human schistosomiasis. The miracidium is the first infective stage in the complex life cycle of schistosomes. The future of the entire life cycle depends on the capacity and ability of this organism to locate and enter a suitable snail host for further development, Little is known about the nervous system of the miracidium of Schistosoma mansoni and of other trematodes. Studies indicate that miracidia contain a well developed and complex nervous system that may aid the larvae in locating and entering a susceptible snail host (Wilson, 1970; Brooker, 1972; Chernin, 1974; Pan, 1980; Mehlhorn, 1988; and Jones, 1987-1988).

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A freeze-fracture-etched study of the physarum polycephalum plasma membrane during early formation of the macroplasmodial stage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147570 ◽

1993 ◽

Vol 51 ◽

pp. 346-347

Author(s):

Randolph W. Taylor ◽

Henrie Treadwell

Keyword(s):

Plasma Membrane ◽

Life Cycle ◽

Growth Phase ◽

Filter Paper ◽

Physarum Polycephalum ◽

Freeze Fracture ◽

Petri Dish ◽

Wire Screen ◽

Wide Mouth ◽

Sterile Filter

The plasma membrane of the Slime Mold, Physarum polycephalum, process unique morphological distinctions at different stages of the life cycle. Investigations of the plasma membrane of P. polycephalum, particularly, the arrangements of the intramembranous particles has provided useful information concerning possible changes occurring in higher organisms. In this report Freeze-fracture-etched techniques were used to investigate 3 hours post-fusion of the macroplasmodia stage of the P. polycephalum plasma membrane.Microplasmodia of Physarum polycephalum (M3C), axenically maintained, were collected in mid-expotential growth phase by centrifugation. Aliquots of microplasmodia were spread in 3 cm circles with a wide mouth pipette onto sterile filter paper which was supported on a wire screen contained in a petri dish. The cells were starved for 2 hrs at 24°C. After starvation, the cells were feed semidefined medium supplemented with hemin and incubated at 24°C. Three hours after incubation, samples were collected randomly from the petri plates, placed in plancettes and frozen with a propane-nitrogen jet freezer.

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