摘要:

Anomalous secondary thickening occurs in the main axis ofBougainvillea spectabilisas a result of a primary thickening meristem which differentiates in pericycle. The primary thickening meristem first appears in the base of the primary root about 6 days after germination and differentiates acropetally as the root elongates. It begins differentiating from the base of the hypocotyl toward the shoot apex about 33 days after germination. The primary thickening meristem is first observable at the base of the first internode about 60 days after germination. It then becomes a cylinder in the main axis of the seedling. No stelar cambial cylinder forms in the primary root, hypocotyl, or stem because vascular cambium differentiation occurs neither in the pericycle opposite xylem points in the primary root nor in interfascicular parenchyma in the hypocotyl or stem. The primary vascular system of the stem appears anomalous because an inner and an outer ring of vascular bundles differentiate in the stele. Bundles of the inner ring anastomose in internodes, whereas those of the outer ring do not. Desmogen strands each of which is composed of phloem, xylem with both tracheids and vessels, and a desmogic cambium, differentiate from prodesmogen strands in conjunctive tissue. The parenchymatous cells surrounding desmogen strands then differentiate into elongated simple‐pitted fibers and thick‐walled fusiform cells that are about the same length as the primary thickening meristem initials.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10190.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06011.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The effects of the endogenous “senescence factor” (SF) and synthetic (±)‐abscisic acid (ABA) on basipetal transport of indoleacetic acid (IAA) inColeus blumeiBenth. were studied. When used to pretreat explant petioles, both SF and ABA accelerated abscission and decreased basipetal movement of IAA through petiolar sections but had no effect on acropetal movement, which was negligible in all experiments. SF decreased the intensity but not the velocity of the basipetal movement of IAA. Pretreatment with either SF or ABA decreased the free IAA and increased the IAA‐aspartate extractable from the sections. The results support the hypothesis that SF and ABA hasten abscission by lowering the amounts of IAA transport in the tissue. Known properties of SF are similar to those of ABA. Efforts are under way to elucidate the chemical identity of SF.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10191.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06013.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

A classification of the architectural features of dicot leaves—i.e., the placement and form of those elements constituting the outward expression of leaf structure, including shape, marginal configuration, venation, and gland position—has been developed as the result of an extensive survey of both living and fossil leaves. This system partially incorporates modifications of two earlier classifications: that of Turrill for leaf shape and that of Von Ettingshausen for venation pattern. After categorization of such features as shape of the whole leaf and of the apex and base, leaves are separated into a number of classes depending on the course of their principal venation. Identification of order of venation, which is fundamental to the application of the classification, is determined by size of a vein at its point of origin and to a lesser extent by its behavior in relation to that of other orders. The classification concludes by describing features of the areoles, i.e., the smallest areas of leaf tissue surrounded by veins which form a contiguous field over most of the leaf. Because most taxa of dicots possess consistent patterns of leaf architecture, this rigorous method of describing the features of leaves is of immediate usefulness in both modern and fossil taxonomic studies. In addition, as a result of this method, it is anticipated that leaves will play an increasingly important part in phylogenetic and ecological studies.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10192.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06014.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06015.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06016.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06017.x

出版商:Wiley    

年代:1973

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb06018.x

出版商:Wiley    

年代:1973

数据来源: WILEY