摘要:

ZusammenfassungDie Salzdrüsen der GattungLimoniumleiten sich ontogenetisch von einer einzelnen epidermalen Zelle ab, die sich in fünf Teilungsschritten zu einem 20‐zelligen Drüsenkomplex differenziert. Die Cutinisierung des Drüsenkomplexes erfolgt bereits nach dem vierten Teilungsschritt bei der Bildung der vier Sammel‐ und der vier Bechermutterzellen. Diese werden durch den fünften Teilungsschritt in innere und äußere Becherzellen geteilt.AbstractTheLimonium‐salt gland develops from only one epidermal cell in five steps of cell‐division to a gland complex of 20 cells. Cutinisation on the gland complex starts after the fourth step of cell‐division, when four collecting cells and four mother cells of the cup cells are formed. In the last step the mother cup cells divide into four inner cup cells and four

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBiophysical considerations allow estimates of the mechanical stresses on self‐bearing vertical stems of plants. Even at moderate wind velocities the stresses induced by aerodynamic forces dominate over those induced by the own weight. Using polar coordinates, analytical expressions of cross‐sectional area and axial second moment of area for centrisymmetric structures with symmetries threefold or higher are derived. Calculating the relative section modulus for various (centrisymmetric) arrangements of stabilizing structures leads to an estimate of the “mechanical effectivity” of these structures. If for plant stems, seen as composite materials, the second moments of area and the elastic moduli are known, the contribution of the different tissues to mechanical stability can be determined quantitatively. The mechanical design of early “vascular” land plants and of stems of (fossil) trees and lianas in different ontogenetic stages can

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractHollow plant stems are, compared to solid ones, endangered by a particular kind of mechanical damage: local buckling. In upright stems centric forces due to the weight of the plant itself are not critical. Bending, however, as caused by wind forces causes transverse stresses that lead to local buckling, long before the critical tension or compression stresses are reached.A new numerical method is proposed to treat local buckling of hollow plant stems caused by bending forces. The results emphasize the importance of transverse reinforcements in the nodes and/or the nodal thickenings for the stability of hollow structures.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1990.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY