Document Type

Thesis - Open Access

Award Date

1956

Degree Name

Master of Science (MS)

Department

Botany

Abstract

The number and nature of stamens in flowers of the Curcurbitaceae has long been a controversial problem among students of floral morphology. Naudin 1885, according to Chakvarty (2), thought that 3 was the basic number of stamens in this family. Naudin imagined a 2-2-1 stamen arrangement where 2 is a complete stamen (tetrasporangiate), and 1 is a half-stamen (bisporangiate). In the few species of this family which have five stamens, he believed that the two complete stamens split resulting in what he called four half-stamens. These, together with the normal half-stamen, would account for the total of five, each bearing two sporangia. Payer 1857, according to Miller (10), “presented the opposing view, that the small bisporangiate stamen was normal, while the large tetrasporangiate stamen had resulted from the union of two normal ones”. Miller cites other investigators through the latter half of the nineteenth century, whose papers were not available to this writer. These workers, however, sided either with Naudin or Payer in their interpretations. More recently Heimlich (6), in his study of the flowers of cucumber, agreed with Naudin’s earlier work, calling one stamen of the flower a half-stamen. In 1928 Miller (10) investigated the staminate flower of Echinocysitis lobate, and he came to close agreement with Payer. Miller found that there are only two stamens in the staminate flower of this species; one tetrasporangiate and one bisporangiate. But he showed the evidence that there are fundamentally three stamens, each bisporangiate; but that two of them become united during their early development, appearing finally as one tetrasporangiate stamen. Chakvarty (2) who has most recently worked on the stamen situation in Cucurbitaceae, agreed with Miller’s interpretation, and suggested further that reduction from pentamery to trimary in the family was due to fusion. He did not accept the half-stamen idea either. In the foregoing investigations of cucurbitaceous stamens, little attention has been given to the staminodia in the pistillate flowers. With a suspicion that the staminodium situation might reveal some primitive relationships among stamens, this present investigation of staminodia was undertaken. Once the matter is cleared up, it should contribute to the working knowledge of both taxonomists and morphologists. Moreover, study of the nature and degree of development of staminodia in Echinocystis lobate may prove helpful to our understanding of the separate sexes among many flowering plants. Literature does not mention that the pistillate flower of Echinocystis lobate may produce pollen grains, but it should be mentioned that in some pistillate flowers the author did find functioning “stamens” with apparently normal pollen. In his studies on sex balance in squesh, Nitsch (11) found that more pistillate flowers were produced at low temperatures than at high temperatures; and that artificially increasing the length of day, consistently retarded production of pistillate flowers, so that the sex balance swayed toward maleness. Since the flower specimens for the present investigation of Echinocystis lobate were collected in early September, when days were still long and temperatures still high, the occurrence of occasional functioning stamens in pistillate flowers may well be another instance of the trend toward maleness which Nitsch describes. A study of the effect of light and temperature on the development of stamens in the pistillate flower of Echinocystis lobate, would be a promising problem for physiologists.

Library of Congress Subject Headings

Echinocystis lobata -- Morphology
Echinocystis lobata -- Anatomy

Description

Includes bibliographical references (page 21)

Format

application/pdf

Number of Pages

26

Publisher

South Dakota State University

Rights

No Copyright - Non-Commercial Use Only
http://rightsstatements.org/vocab/NoC-NC/1.0/

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