The Development of the Vascular System in Evergreen Leaves More than One Year Old

Elliott, Jordana

doi:10.1093/oxfordjournals.aob.a083450

Cited by 26 publications

(18 citation statements)

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“…Elliott (1937) reported that secondary xylem was present without secondary phloem in the leaves of 3 of 13 evergreen dicotyledonous species he examined. Although secondary growth is more commonly associated with stems and roots, it is not unknown in leaves, especially long-lived leaves of evergreen species.…”

Section: Results-heteroblastic Leaf Series In Sap-mentioning

confidence: 99%

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

Steingraeber

Fisher

1986

American J of Botany

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Leaves of seed plants are generally characterized as organs of determinate growth. In this regard, Guarea and related genera seem unusual in that the pinnately compound leaves of these plants contain a bud at their tip from which new pinnae expand from time to time. Previous studies (based upon superficial examinations of leaf‐tip buds) have produced contradictory conclusions regarding how long the leaf apex remains meristematic and produces new pinna primordia. In order to determine whether leaf development in Guarea is truly indeterminate, we microscopically examined leaf‐tip buds of G. guidonia and G. glabra. In both species, the leaf apex remains meristematic and continues to produce new pinna primordia as the leaf ages. Unexpanded leaves of G. guidonia contained an average of 23 pinna primordia, while the oldest leaves we examined had initiated an average of 44 total pinnae. In G. glabra, unexpanded leaves contained 8 pinnae, whereas an average of 28 pinnae had been initiated on the oldest leaves. These results indicate that leaf development in Guarea is truly indeterminate. Periodic examination of individual intact leaves indicated that the leaves commonly continue their growth for 2 or more years (observed maximum = 51 months). As new leaflets are initiated at the shoot apex (and subsequently expand in rhythmic flushes), older (basal) leaflets may abscise. In addition, the petiole and rachis of the leaf thicken and become woody as a result of the activity of a vascular cambium. Guarea leaves therefore seem to function as the analogue of a typical twig (stem) in general habit as well as in their indeterminate apical growth and secondary thickening.

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Section: Results-heteroblastic Leaf Series In Sap-mentioning

confidence: 99%

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

Steingraeber

Fisher

1986

American J of Botany

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“…This phenomenon begins as early as the first year, but only becomes marked from the fifth year onwards. The flattening of the most peripheral phloem cells is a process that has been known for some time (Elliott 1937), but it is only recently that the early onset of the phenomenon has been related to forest decline (Fink 1983(Fink , 1987(Fink , 1988b(Fink , 1989Parameswaran et al 1985;.…”

Section: Discussionmentioning

confidence: 99%

Leaf phloem alterations in two provenances ofAbies alba Miller (silver fir) during ageing

Bottacci

Lippi

Tani

et al. 1995

Trees

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Abstract. The phenomenon of premature needle senescence in two Italian provenances of silver fir was studied as part of a more general research project on declining Abies alba. The two provenances showed a different degree of sensitivity to atmospheric pollutants. Comparative observations on 1-, 3-, 5-, 7-and 9-year-old needles from both provenances highlighted a faster loss of function in the phloem of needles from the Vallombrosa provenance. This fact appears to be related more to a loss of function in the cambium, than to a different rate of degeneration of sieve cells. This phenomenon may help explain why needles of the Vallombrosa provenance tend to be shed sooner than those of the Serra San Bruno provenance.

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“…In such cases, however, the vascular cambium commonly is unidirectional and produces either secondary xylem or secondary phloem. Elliott (1937) reported that secondary xylem was present without secondary phloem in the leaves of 3 of 13 evergreen dicotyledonous species he examined. In leaves of evergreen conifers, a unidirectional cambium produces secondary phloem without secondary xylem (Ewers, 1982).…”

Section: Secondary Growth Ofthe Petiole and Rachis-mentioning

confidence: 99%

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

Steingraeber

Fisher

1986

American Journal of Botany

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Leaves of seed plants are generally characterized as organs of determinate growth. In this regard, Guarea and related genera seem unusual in that the pinnately compound leaves ofthese plants contain a bud at their tip from which new pinnae expand from time to time. Previous studies (based upon superficial examinations of leaf-tip buds) have produced contradictory conclusions regarding how long the leaf apex remains meristematic and produces new pinna primordia. In order to determine whether leaf development in Guarea is truly indeterminate, we microscopically examined leaf-tip buds of G. guidonia and G. glabra. In both species, the leaf apex remains meristematic and continues to produce new pinna primordia as the leaf ages. Unexpanded leaves of G. guidonia contained an average of23 pinna primordia, while the oldest leaves we examined had initiated an average of 44 total pinnae. In G. glabra, unexpanded leaves contained 8 pinnae, whereas an average of 28 pinnae had been initiated on the oldest leaves.These results indicate that leaf development in Guarea is truly indeterminate. Periodic examination of individual intact leaves indicated that the leaves commonly continue their growth for 2 or more years (observed maximum = 51 months). As new leaflets are initiated at the shoot apex (and subsequently expand in rhythmic flushes), older (basal) leaflets may abscise. In addition, the petiole and rachis of the leaf thicken and become woody as a result of the activity of a vascular cambium. Guarea leaves therefore seem to function as the analogue of a typical twig (stem) in general habit as well as in their indeterminate apical growth and secondary thickening. 1971). The angiosperm leaf is therefore considered to be an organ of determinate growth, while stems characteristically exhibit indeterminate growth (Esau, 1965;Foster and Gifford, 1974). This contrasts with the pattern of leaf development exhibited by some ferns (e.g., Lygodium), in which leaves show prolonged apical meristematic activity and, therefore, an indeterminate pattern of growth (Sporne, 1966;Mueller, 1982a Mueller, , b, 1983.Within the angiosperms, an exception to the I

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The Development of the Vascular System in Evergreen Leaves More than One Year Old

Cited by 26 publications

References 0 publications

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

Leaf phloem alterations in two provenances ofAbies alba Miller (silver fir) during ageing

Indeterminate Growth of Leaves in Guarea (Meliaceae): A Twig Analogue

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