ISSN:
1432-2048
Keywords:
Carotenoid
;
Chlorophyll fluorescence
;
Photosynthesis
;
Rehydration respiration
;
Variable-fluorescence decrease ratio
;
Xerophyta
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Resynthesis of the photosynthetic apparatus and resumption of CO2 assimilation upon rehydration is reported for the monocotyledonous and poikilochlorophyllous desiccation-tolerant (PDT) plant Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae). During desiccation there was a complete breakdown of chlorophylls whereas the total carotenoid content of air-dried leaves was reduced to about 22% of that of functional leaves. The prerequisites for the resynthesis of photosynthetic pigments and functional thylakoids were the reappearance of turgor and maximum leaf water content at 2 and 10 h after rehydration, respectively. The period of increased initial respiration after rewetting leaves (rehydration respiration) lasted up to 30 h and was thus 6 to 10 times longer than in homoiochlorophyllous desiccation-tolerant plants (HDTs) in which chlorophylls are retained during desiccation. Accumulation of chlorophylls a + b and total carotenoids (xanthophylls and βcarotene) started 10 h after rehydration. Normal levels of chlorophyll and carotenoids were obtained 72 h after rehydration. Values for the variable-fluorescence decrease ratio (Rfd690 values), an indicator of photochemical activity, showed that photochemical function started 10 h after rehydration, but normal values of 2.7 were reached only 72 h after rehydration. Net CO2 assimilation started 24 h after rewetting and normal rates were reached after 72 h, at the same time as normal values of stomatal conductance were obtained. The increasing rates of net CO2 assimilation were paralleled by decreasing values of the intercellular CO2 concentration. All photosynthetic parameters investigated showed values normal for functional chloroplasts by 72 h after the onset of rehydration. Fully regreened leaves of the presumed C3 plant X. scabrida exhibited a net CO2 assimilation rate which was in the same range as that of other C3 plants and higher than that of recovered HDT plants. The fundamental difference between air-dried PDT plants, such as X. scabrida, which have to resynthesize the photosynthetic pigment apparatus, and air-dried HDT plants, which only undergo a functional recovery, is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00198578
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