Effect of night chilling on photosynthesis of two coffee species grown under different irradiances
The effect of night chilling on the photosynthetic physiology of seedlings of two coffee species (Coffea arabica and C. liberica) was investigated. The coffee seedlings were grown in pots in a fully-open site, and in a shade plot of 50 percent daylight forboth coffee species, and in shade plots with two additional irradiance regimes of 8 and 25 percent daylight for C. liberica. In January 2003, the seedlings were moved to a cold storage room at 4 deg C overnight for three consecutive nights and returned to theiroriginal places during the day. Gas exchange rates were measured in the late morning, and chlorophyll a fluorescence was measured at dawn and midafternoon during the day before chilling and after days with the chilling treatment and the subsequent 3 daysafter chilling. Chlorophyll, carotenoid and MDA (malondialdehyde) contents were determined from the leaves of the coffee seedlings on the day before and the third day with the chilling treatment. Night chilling induced rapid decreases in gas exchange rates and decreases in maximum photochemical efficiency of photosystem II (Fv/Fm), and increases of both minimum fluorescence yield (Fo) and nonphotochemical quenching (NPQ) for both species; these decreases and increases were usually stronger in seedlings grown in higher irradiances. The decrease of Fv/Fm and increase of Fo were stronger in C. liberica than in C. arabica. C. arabica reached significantly greater NPQ values than C. liberica. Night chilling decreased chlorophyll content and increased the carotenoid to chlorophyll ratio and MDA content in both species under all irradiances. After termination of the chilling treatment, the recovery of gas exchange rates, Fv/Fm, and Fo were much quicker in C. arabica than inC. liberica. Night chilling induced a more severe photoinhibition, and its recovery was slower in C. liberica than in C. arabica. This is consistent with the distribution of the two species: C. liberica is cultivated in tropical lowlands, while C. arabica is cultivated at higher elevations. Shading significantly alleviated chilling-induced photoinhibition.
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| Format: | biblioteca |
| Published: |
2004
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| Subjects: | COFFEA, COFFEA ARABICA, COFFEA LIBERICA, CAROTENOIDES, COMPOSICION QUIMICA, CLOROFILAS, CAFE, FRIO, INTERCAMBIO DE GASES, IRRADIACION, FOTOINHIBICION, FOTOSINTESIS, PLANTULAS, SOMBRA, ANGIOSPERMAS, SPERMATOPHYTA, |
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