Titlebar

Export bibliographic data
Literature by the same author
plus on the publication server
plus at Google Scholar

 

Sequence of morphological and physiological events during natural ageing and senescence of a castor bean leaf : Sieve tube occlusion and carbohydrate back-up precede chlorophyll degradation

Title data

Jongebloed, Udo ; Szederkényi, Judit ; Hartig, Katja ; Schobert, Christian ; Komor, Ewald:
Sequence of morphological and physiological events during natural ageing and senescence of a castor bean leaf : Sieve tube occlusion and carbohydrate back-up precede chlorophyll degradation.
In: Physiologia Plantarum. Vol. 120 (2004) Issue 2 . - pp. 338-346.
ISSN 1399-3054
DOI: https://doi.org/10.1111/j.0031-9317.2004.0245.x

Abstract in another language

The development of castor bean (Ricinus communis L. var. sanguineus) leaves from bud break to abscission was studied to determine whether senescence of phloem precedes or follows chlorophyll degradation in the course of natural ageing of leaves. The castor bean leaf blade took 20 days for full expansion and its average life span was 60 days. From the day of full expansion on it suffered a substantial loss in N, a small loss in C, K and P and a gain in Ca, Mg and S. The content of soluble sugars increased with time, paralleled by a decrease of photosynthetic activity. Starch accumulated shortly before chlorophyll breakdown. The amino acid level in the leaves decreased steadily together with nitrate reductase and glutamine synthetase activity. Reactive oxygen species increased and oxidation-protecting compounds decreased during the life span of the leaves. Shortly after full leaf expansion an increasing number of sieve plates showed strong callose depositions when visualized by aniline blue method. At day 40 only half of the sieve tubes appeared functional. Chlorophyll breakdown followed these processes with a time lag of approximately 10 days. The sieve tube sap of ageing leaves had the same sucrose concentrations as young leaves, whereas amino acid concentrations decreased. High levels of reduced ascorbic acid and glutathione together with increasing levels of glutaredoxin indicated oxidative strain during senescence. We speculate that the gradual increase of reactive oxygen species during ageing together with the import of calcium ions lead to the stimulation of callose synthesis in plasmodesmata and sieve plates with the consequence of inhibition of phloem transport leading to carbohydrate back-up in the leaf blade. The latter may finally induce chlorophyll breakdown and, at the end, leaf abscission at the petiole base. Thus phloem blockage would precede and may be causal for chlorophyll degradation in leaf senescence.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER77506
BAYCEER22423
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Plant Physiology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 21 Aug 2015 06:49
Last Modified: 21 Aug 2015 06:49
URI: https://eref.uni-bayreuth.de/id/eprint/18511