Authors: Abreu, Maria Elizabeth; Munné-Bosch, Sergi

Source: Physiologia Plantarum, Volume 134, Number 2, October 2008 , pp. 369-379(11)

Publisher: Wiley-Blackwell

Abstract:

The influence of leaf angle on the response of plants to high light was studied in Salvia broussonetii, a species endemic of the Canary Islands that shows hyponastic leaf growth. The response of vertical, naturally oriented leaves was compared with that of horizontal, artificially held leaves for 1, 13, 24 and 29 days in terms of photoinhibition [efficiency of photosystem II (PSII)], photoprotection (by the xanthophyll cycle, α-tocopherol and β-carotene) and progression of leaf senescence. Vertical leaves not only showed a decreased photoprotective demand compared with horizontal leaves but also kept the maximum efficiency of PSII (F_v/F_m ratio) constant throughout the experiment, thus reflecting the capacity of naturally oriented leaves to avoid photooxidative stress in the field. By contrast, horizontal leaves, which were exposed to higher light intensities, showed a higher photoprotective demand (reflected by a higher de-epoxidation of the xanthophyll cycle, carotenoid losses and increases in α-tocopherol), damage to PSII (as indicated by decreases in the F_v/F_m ratio) and accelerated leaf senescence, which was associated with cell death after 24 days of high light exposure. It is concluded that hyponastic leaf growth prevents photoinhibition and decreases the photoprotective demand of leaves by reducing the incident light, which helps maintaining leaf vigor and delaying the progression of leaf senescence in S. broussonetii plants. Hyponastic leaf growth is therefore one of the first photoprotection mechanisms activated in this species to avoid the negative impact of high-light stress in the field.

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1399-3054.2008.01144.x

Affiliations: 1: Departament de Biologia Vegetal, Universitat de Barcelona, Facultat de Biologia, Avinguda Diagonal 645, 08028 Barcelona, Spain

Publication date: 2008-10-01

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