Studies on Foliar Epidermis in Primitive Genera of Rosaceae and Its Systematic Significance

Abstract

Abstract:

n order to provide additional evidence of the phylogenetic relationships

between genera of Rosaceae, it is neccessary to study and analyse the characters in primitive

genera of the family. In this paper, leaf epidermis of the primitive genera of Rosaceae, inc-

luding Kagneckia, Quillaja, Vauquelinia, Lindleya, Exochorda and Lyonothamus of Trib.

Quillajeae circumscribed by Hutchinson (1964), has been anatomically studied and description

of epidermal structure is presented. Several types of stomatal apparatuses have been observed

in the genera investigated and considered as having systematic significance at generic level.

(I) On the basis of the foliar epidermal characters, the following key to the genera is

presented:

1. Stomatal apparatuses polytypic, of 2-3 types

2. Polytypic stomatal apparatuses incruding 3 types, anomocytic, actinocytic and staurocytic.

3. Polytypic stomatal apparatuses only of 2 types, anomocytic and actinocytic, with the

former dominant and surrounding the latter ...... 1. Kagneckia Ruiz & Pav.

3. Polytypic stomatal apparatuses of 3 types, anomocytic, actinocytic and staurocytic

4. Stomatal apparatuses sparse, with anomocytic and actinocytic ones dominant. .......

..................................................................... 3. Exochorda Lindl.

4. Stomatal apparatuses dense, with staurocytic type dominant. .........................

........................................................... 4. Lindleya H. B. & K. Nov.

2. Polytypic stomatal apparatuses of 2 types, paracytic and cyclocytic, subsidiary cells

narrow and distinguishable from other epidermal cells. ................ 2. Quillaja Molina

1. Stomatal apparatus monotypic, almost only actinocytic.

5. Guard cells surrounded radically by 7-9 subsidiary cells equal in diam. .......

....................................... 5. Vauquelinia Gorrea ex Humb & Bongl.

5. Guard cells sunkes, 19.76-30.70μm deep, adaxiaL wall of elongated subsidiary cells

so united transversely and thickened that the whole stomatal apparatus pot-like, stomatal ap-

paratuses aggregated in a mass and having no any ordinary epidermal cells among them...

........................................................................... 6. Lyonothamus A. Gray

(II) In the most primitive extant genus, Kagneckia, the stomatal apparatuses are ma-

inly the most primitive anomocytic, but also actinocytic.

(III) In another primitive genus, Quillaja, only second to and most related to the genus

Kagneckia, there are both paracytic and cyclocytic types of stomatal apparatuses, some subsi-

diary cells of which are partly overlapped by the guard cells so that they appear very narrow

in surface view. Based on the study of the most primitive genus, Kagneckia, and the second

primitive genus, Quillaja, it seems that the paracytic type of stomatal apparatus may be de-

rived from the anomocytic one in Rosaceae.

(IV) The stomatal apparatus, in the genus Vauquelinia are actinocytic and undoubtedly

derived from that in the more primitive rosoids.

(V) The pot-like stomatal apparatuses in the genus Lyonothamus are very unique and_

apparently more specialized. Morphologivally, in the genus, there are opposite, fern-like lea-

ves and the pistil consists of only 2. carpels It may be a very isolated relict along the coast of

California in N. America.

(VI) In the genus Exochorda, although anomocytic and actinocytic stomatal apparatuses

are dominant, staurocytic type also occurs. Morphologically, the genus is more advanced than

Kagneckia and Quillaja. In the genus Lindleya, there are also anomocytic and actinocytic types

of stomatal, apparatuses, though staurocytic type is dominant. The genus Lindleya is also

morphologically more advanced than the most primitive genera of Rosaceae mentioned above.

The studies support the inferrence from cytology (Goldblatt 1976) that the tribe Quilla-

jeae in Rosaceae is an unnatural alliance.

Acknowledgement The author wishes to express his thanks to Dr. Stevens, who was

the supervisor of the Harvard University Herbaria, for allowing me to collect the materials

investigated during my stay in the herbaria from 1982 to 1984.

Li Chao-Luan. Studies on Foliar Epidermis in Primitive Genera of Rosaceae and Its Systematic Significance[J]. .

Studies on Foliar Epidermis in Primitive Genera of Rosaceae and Its Systematic Significance

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