Fluxo de seiva e fotossíntese em laranjeira 'Natal' com clorose variegada dos citros

The objective of this work was to evaluate the effects of citrus variegated chlorosis (CVC) on sap flow, gas exchanges and photochemical activity in 'Natal' sweet orange plants with and without CVC under field condition. Diurnal courses of sap flow, leaf water potential, CO2 assimilation rate and transpiration, stomatal conductance, potential and effective quantum efficiency of photosystem II were evaluated. The experiment was arranged in a random block design with five repetitions. Healthy plants showed sap flow values around 1.9 times higher than injured ones. Injured plants exhibited reductions of 43, 28 and 33% in CO2 assimilation rate, stomatal conductance and leaf transpiration, respectively. CVC-affected plants showed dynamic photoinhibition. Since healthy and injured plants showed similar diurnal course of effective quantum efficiency, the possible influence of photorespiration on photochemical apparatus in CVC-affected plants is discussed. Reductions in CO2 assimilation rate, transpiration and sap flow of injured plants were induced by low stomatal conductance values, which was probably due to the xylem vessel colonization by Xylella fastidiosa.

[1]  J. Hartung,et al.  Specific PCR detection and identification of Xylella fastidiosa strains causing citrus variegated chlorosis , 1995, Current Microbiology.

[2]  D. Hopkins,et al.  Fastidious xylem-limited bacterial plant pathogens. , 1996, Annual review of phytopathology.

[3]  E. C. Machado,et al.  TROCAS GASOSAS E RELAÇÕES HÍDRICAS EM LARANJEIRAS COM CLOROSE VARIEGADA DOS CITROS , 1994 .

[4]  S. L. Steinberg.  A Gauge to Measure Mass Flow Rate of Sap in Stems and Trunks of Woody Plants , 1989, Journal of the American Society for Horticultural Science.

[5]  Eva Rosenqvist,et al.  Applications of chlorophyll fluorescence can improve crop production strategies: an examination of future possibilities. , 2004, Journal of experimental botany.

[6]  Ulrich Schreiber,et al.  Determination of the quantum efficiency of photosystem II and of non-photochemical quenching of chlorophyll fluorescence in the field , 1995, Oecologia.

[7]  F. Loreto,et al.  THERMOINHIBITION OF PHOTOSYNTHESIS AS ANALYZED BY GAS EXCHANGE AND CHLOROPHYLL FLUORESCENCE , 1998 .

[8]  Park S. Nobel,et al.  Physicochemical and Environmental Plant Physiology , 1991 .

[9]  Luiz Roberto Angelocci,et al.  APLICAÇÃO DO MÉTODO DE BALANÇO DE CALOR NA DETERMINAÇÃO DA TRANSPIRAÇÃO DE MUDAS DE LIMOEIRO , 1997 .

[10]  Tetsuo Sakuratani,et al.  A heat balance method for measuring water flux in the stem of intact plants , 1981 .

[11]  E. Machado,et al.  CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa , 2003 .

[12]  F. Marin,et al.  Transpiration, leaf diffusive conductance, and atmospheric water demand relationship in an irrigated acid lime orchard , 2004 .

[13]  R. V. Ribeiro,et al.  Growth- and leaf-temperature effects on photosynthesis of sweet orange seedlings infected with Xylella fastidiosa , 2004 .

[14]  E. Alves,et al.  Leaf symptoms on plum, coffee and citrus and the relationship with the extent of xylem vessels colonized by Xylella fastidiosa , 2004 .

[15]  E. Machado,et al.  Gas exchange rates at different vapor pressure deficits and water relations of ‘Pera’ sweet orange plants with citrus variegated chlorosis (CVC) , 2003 .

[16]  R. V. Ribeiro,et al.  High temperature effects on the response of photosynthesis to light in sweet orange plants infected with Xylella fastidiosa , 2003 .

[17]  J. Briantais,et al.  The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence , 1989 .

[18]  A. McElrone,et al.  Interactive effects of water stress and xylem-limited bacterial infection on the water relations of a host vine. , 2003, Journal of experimental botany.

[19]  A. Hall,et al.  Temperature and Humidity Effects on Net Photosynthesis and Transpiration of Citrus , 1976 .

[20]  R. V. Ribeiro,et al.  Early photosynthetic responses of sweet orange plants infected with Xylella fastidiosa , 2003 .