Abstract

PENA-OLMOS, Jaime Ernesto  and  CASIERRA-POSADA, Fánor. Chlorophyll Fluorescence in Partially Defoliated Grape Plants (Vitis vinifera L. cv. Chardonnay). Rev. Fac. Nac. Agron. Medellín [online]. 2013, vol.66, n.1, pp.6881-6889. ISSN 0304-2847.

The chlorophyll content and fluorescence were determined in five-year-old grape plants (Vitis vinifera L. cv. Chardonnay) that were subjected to early partial defoliation, in Villa de Leyva, Colombia. The experimental design was completely randomized, consisting of two treatments (50% defoliation and control), each with four replications of 35 plants. Every two weeks, one of every two recently-emerged leaves was removed from the non-control plants. The determination of total chlorophyll content was carried out on six leaves per plant using a CCM-200 Plus chlorophyll meter, while chlorophyll fluorescence measurements were taken with one darkadapted leaf per plant using a Junior-PAM fluorometer. Initial fluorescence (F_o), maximum fluorescence (Fm), terminal fluorescence (F_t), variable fluorescence (F_v), electron transport rate (ETR), maximum photochemical quantum yield of PSII (Fv/ F_m), effective photochemical quantum yield of photosystem II (Y(II)), photochemical fluorescence quenching coefficient (qP), two non-photochemical quenching coefficients (qN and NPQ), quantum yield of light-induced non-photochemical fluorescence quenching (Y(NPQ)), and quantum yield of non-light-induced non-photochemical quenching (Y(NO)) were measured. The chlorophyll concentration index showed higher values in the defoliated plants. There were no significant differences for the values of F_m, F_t and F_v. F_o was higher in the defoliated plants, while ETR, F_v/F_m and Y(II) showed higher values in the control plants. It is evident that a reduction in leaf area modifies the partitioning of excitation energy destined for photochemical and non-photochemical processes, thus directly influencing the photosynthetic process of the plants evaluated.

Keywords : Maximum photochemical quantum yield; Y(II); stress; PSII.

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