Morphological Development of the North American Pawpaw during Germination and Seedling Emergence

The North American pawpaw [Asimina triloba (L.) Dunal], a temperate member of the Annonaceae, is a deciduous woody tree with ornamental value and has merit as a fruit crop. Anatomical studies of pawpaw seed revealed a small, linear embryo that does not change in length during cold or warm stratification. Radicle and cotyledon growth from planting until radicle protrusion was concurrent and at about the same rate. Cotyledons grew through a specialized channel of cells extending above the cotyledon tips, but never emerged from the seed. The extended period of time required for the development of the cotyledons delayed seedling emergence more than 50 days. The cotyledons appear to be haustorial and translocate storage material from the endosperm to the growing embryo. At the time of epicotyl elongation, the radicle and developing root system were well developed and comprised 81 % of the seedling biomass. Seedling development could be divided into four distinct stages, including radicle protrusion, hypocotyl emergence, epicotyl elongation, and seedcoat abscission.

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Morphological Development of Pawpaw [Asimina triloba (L.) Dunal] during Seed Germination and Seedling Emergence

HortScience ◽

10.21273/hortsci.31.4.633c ◽

1996 ◽

Vol 31 (4) ◽

pp. 633c-633

Author(s):

C.L.H. Finneseth ◽

Desmond R. Layne ◽

R.L. Geneve

Keyword(s):

Seed Germination ◽

Developmental Stages ◽

Scientific Information ◽

Seedling Emergence ◽

Dry Weight ◽

Morphological Development ◽

Asimina Triloba ◽

Radicle Protrusion ◽

Total Dry Weight ◽

Food Reserves

Little scientific information is available describing morphological development of pawpaw during seed germination. To provide this information, a study was designed to outline important developmental stages and describe seedling characteristics within each stage. Stratified pawpaw seeds were sown in vermiculite and germinated at 25°C in a growth chamber. Ten seedlings were randomly chosen and destructively harvested at 5-day intervals starting at radicle protrusion. Length (mm), fresh and dry weight, and percentage of total dry weight were determined for seedling components. Pawpaw seeds have a small rudimentary embryo with all food reserves stored in a ruminate endosperm. Dry weight measurements showed a dramatic reallocation of reserves from the storage tissue to developing seedling parts. Initial embryo length was less than 3 mm, but within 70 days seedlings exceeded 350 mm. Twelve days after planting, simultaneous radicle and cotyledon growth occurred (3.4 and 3.0 mm, respectively), but neither hypocotyl nor epicotyl was visible. Radicle protrusion was observed at 15 days with radicle, cotyledon and hypocotyl lengths increasing to 4.4, 4.0, and 3.2 mm, respectively. Endosperm comprised 99.1% of total dry weight at this stage. The hypocotyl hook emerged after 30 days and endosperm comprised 76.1% of total dry weight. Cotyledons reached maximum length (29.0 mm) at day 40 and the epicotyl was discernible. At 55 days, the seed coat containing cotyledons and residual endosperm abscised and the average radicle, hypocotyl and epicotyl lengths were 182.0, 61.1, and 7.3 mm, respectively. It is suggested that the cotyledons primary function is absorption of food reserves from the endosperm for transfer to the developing seedling.

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Boreameryx, an unusual new artiodactyl (Mammalia) from the Pliocene of Arctic Canada and endemism in Arctic fossil mammals

Canadian Journal of Earth Sciences ◽

10.1139/e06-111 ◽

2007 ◽

Vol 44 (5) ◽

pp. 585-592 ◽

Cited By ~ 3

Author(s):

Mary R Dawson ◽

C R Harington

Keyword(s):

North American ◽

Ellesmere Island ◽

Morphological Development ◽

Long Bones ◽

Beaver Pond ◽

Arctic Canada ◽

Posterior Portion ◽

Early Pliocene ◽

Fossil Mammals ◽

The North

Boreameryx braskerudi, gen. et sp. nov., from Early Pliocene (about 5–4 Ma) deposits of Ellesmere Island, Nunavut, is represented by the posterior portion of a dentary with three molars, a partial calcaneum, unciform, and fragments of long bones and ribs. The incompletely known structure of Boreameryx must leave open the questions of its relationships within the pecoran ruminants. Even its possible affinities with early cervoids and the North American blastomerycines are speculative. We favour the tentative association of Boreameryx within the Cervoidea. Rather than evolving hypsodonty to deal with abrasive northern foods, Boreameryx apparently retained plesiomorphic dental structures—even augmenting those structures in a unique morphological development. We hypothesize, based on recorded relationships and ranges (both geological and geographical) of several Beaver Pond site mammals, including Boreameryx, that they indicate a significant interval of endemic development in a high northern biotic province prior to 5 Ma.

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Identification of Annonaceous Acetogenins in the Ripe Fruit of the North American Pawpaw (Asimina triloba)

Journal of Agricultural and Food Chemistry ◽

10.1021/jf9018239 ◽

2009 ◽

Vol 57 (18) ◽

pp. 8339-8343 ◽

Cited By ~ 22

Author(s):

Kirk W. Pomper ◽

Jeremiah D. Lowe ◽

Sheri B. Crabtree ◽

William Keller

Keyword(s):

North American ◽

Ripe Fruit ◽

Annonaceous Acetogenins ◽

Asimina Triloba ◽

The North

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ANOLOBINE, AN ALKALOID FROM ASIMINA TRILOBA DUNAL

Canadian Journal of Research ◽

10.1139/cjr38b-013 ◽

1938 ◽

Vol 16b (3) ◽

pp. 76-80 ◽

Cited By ~ 10

Author(s):

Richard H. F. Manske

Keyword(s):

North American ◽

Phenolic Hydroxyl ◽

Hydroxyl Group ◽

Methylenedioxy Group ◽

Asimina Triloba ◽

The North ◽

Vinyl Compound ◽

Plausible Structure

An alkaloid, for which the name anolobine is now suggested, has been isolated from the bark of Asimina triloba Dunal, the North American papaw. It is best represented by C17H17O3N and contains one phenolic hydroxyl group. Gaebel's reaction indicates a methylenedioxy group. The nitrogen is secondary. Exhaustive methylation and oxidation of the final vinyl compound has yielded 4-methoxyphthalic acid, and this observation together with a knowledge of analogous alkaloids from related plants has made it possible to designate a highly plausible structure for anolobine. A glycoside was found in the leaves although it does not appear to be present in the bark.

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