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TROCAS GASOSAS E RELA??ES HíDRICAS EM LARANJEIRA 'VALêNCIA' ENXERTADA SOBRE LIMOEIRO 'CRAVO' E TRIFOLIATA E SUBMETIDA à DEFICIêNCIA HíDRICA
MEDINA, CAMILO LáZARO;MACHADO, EDUARDO CARUSO;
Bragantia , 1998, DOI: 10.1590/S0006-87051998000100002
Abstract: different rootstocks may influence orange tree tolerance to water stress. under controlled conditions and water deficit, co2 assimilation rate (a), transpiration rate (e), stomatal conductance (gs), water use efficiency (wue), leaf water potential (yl) and relative water content (rwc), were analysed, in potted 2 years old 'valencia' orange trees grafted on 'rangpur' lime and poncirus trifoliata (trifoliata), rootstocks. there was no decrease in a, e, wue, yl and rwc when the substrate water potential (ysb) was above -0.04 mpa. however, when ysb was bellow -0,05mpa, plants grafted on both rootstocks showed different responses. in plants 'rangpur' a, wue and yl started lowering one day before plants on trifoliata and delayed two days to recover. when ysb =-0.13mpa, a reached 4.1 mmol/m2.s and 1.8 mmol/m2.s to trifoliata and 'rangpur' treatments, respectively. the minimum values of a when ysb = 0.23mpa were 1.0 and 2.0 mmol/m2.s in 'rangpur' and trifoliata, respectively. maintenance of the highest values of a, gs, wue and yl suggested that 'valencia' orange tree grafted on potted trifoliata showed a higher tolerance to water stress than that grafted on 'rangpur'.
TROCAS GASOSAS E RELA ES HíDRICAS EM LARANJEIRA 'VALêNCIA' ENXERTADA SOBRE LIMOEIRO 'CRAVO' E TRIFOLIATA E SUBMETIDA à DEFICIêNCIA HíDRICA
MEDINA CAMILO LáZARO,MACHADO EDUARDO CARUSO
Bragantia , 1998,
Abstract: Em citros, diferentes porta-enxertos podem afetar a tolerancia da planta à deficiência hídrica. Neste trabalho, avaliaram-se, sob condi es controladas, as taxas de assimila o de CO2 (A) e de transpira o (E), a condutancia estomática (gs), a eficiência no uso da água (WUE), o potencial da água na folha (Yl) e o conteúdo relativo de água (RWC), em mudas de laranjeira 'Valência' sobre os porta-enxertos limoeiro 'Cravo' e Poncirus trifoliata (Trifoliata) submetidas à deficiência hídrica. As mudas foram cultivadas em vasos e a deficiência hídrica, aplicada pela suspens o da irriga o. N o houve decréscimo em A, E, WUE, Yl e RWC nas plantas quando o potencial da água no substrato (Ysb) esteve acima de -0,04 MPa, mostrando valores semelhantes entre os tratamentos. Para Ysb abaixo de -0,05 MPa, contudo, além de ter ocorrido queda nos valores de A, E, WUE, gs e Yl, as plantas sobre os dois porta-enxertos apresentaram respostas diferentes. As plantas sobre 'Cravo' iniciaram a queda em A, WUE e Yl um dia antes que as plantas sobre Trifoliata e levaram dois dias mais para se recuperarem. Em Ysb de -0,13 MPa, A atingiu 4,1 mmol/m2.s para o tratamento Trifoliata e 1,8 mmol/m2.s para o 'Cravo'. Os valores mínimos de A foram atingidos em Ysb de -0,23 MPa, sendo de 1,0 mmol/m2.s para o 'Cravo' e 2,0 mmol/m2.s para o Trifoliata. A manuten o de maiores valores de A, gs, WUE e Yl, em condi es de limita o ao desenvolvimento do sistema radicular, sugeriu maior tolerancia à deficiência hídrica de laranjeira 'Valência' enxertada sobre Trifoliata que sobre 'Cravo', em plantas em vasos.
FOTOSSíNTESE DE LARANJEIRA 'VALêNCIA' ENXERTADA SOBRE QUATRO PORTA-ENXERTOS E SUBMETIDA à DEFICIêNCIA HíDRICA
MEDINA, CAMILO LáZARO;MACHADO, EDUARDO CARUSO;PINTO, JOSé MARIA;
Bragantia , 1998, DOI: 10.1590/S0006-87051998000100001
Abstract: the co2 assimilation rate and leaf water potential were analyzed in 18-months-old `valencia' orange tree, in pots. the plants were grafted on four different rootstocks: `rangpur' lime, trifoliata, `troyer' citrange and `cleopatra' mandarin. plants were submitted to water stress until the co2 assimilation rate was negligible when they were rehydrated. it was also analysed the hydraulic conductivity of the rootstocks used. under well watered conditions, co2 assimilation rate was lower in plants grafted on `troyer' and `cleopatra' when compared with plants grafted on `cravo' which was not different from plants grafted on trifoliata. throughout the day the greatest co2 assimilation rates were observed by 9:00h, with 8mmol/m2.s, followed by a decrease due possibly to the increase in the vapour water deficit and room temperature, from 11:00h through 14:00h. after withholding water, in the decreasing at the leaf water potential was similar to all the plants, regardless of the rootstocks used. nevertheless, co2 assimilation rate decreased more rapidly, after withholding water, and it was recovered more slowly after rehydration, in plants grafted on `cravo'. these plants also presented, during the entire water deficit period, lower co2 assimilation rate than plants grafted on trifoliata and `cleopatra', and similar to `troyer'. plants grafted on trifoliata recovered co2 assimilation rate in 3 days while those grafted on other rootstocks did not recover entirely in that period. the hydraulic conductivity was higher in `cravo' lemon tree and there were no differences among the values found in the other rootstocks.
FOTOSSíNTESE DE LARANJEIRA 'VALêNCIA' ENXERTADA SOBRE QUATRO PORTA-ENXERTOS E SUBMETIDA à DEFICIêNCIA HíDRICA
MEDINA CAMILO LáZARO,MACHADO EDUARDO CARUSO,PINTO JOSé MARIA
Bragantia , 1998,
Abstract: Avaliou-se a taxa de assimila o de CO2 e o potencial da água nas folhas, em laranjeiras `Valência' com 18 meses de idade, em vasos, enxertadas em quatro tipos de porta-enxertos: limoeiro `Cravo', Trifoliata, citrange `Troyer' e tangerina `Cleópatra'. A deficiência hídrica foi obtida pela suspens o da irriga o até que a taxa de assimila o de CO2 atingisse valores aproximadamente nulos, quando, ent o, foram reirrigadas. Avaliou-se, também, a condutividade hidráulica dos porta-enxertos utilizados. Sem deficiência hídrica, a taxa de assimila o de CO2 foi menor nas plantas sobre os porta-enxertos `Troyer' e `Cleópatra', quando comparadas àquelas plantas sobre limoeiro `Cravo', que n o se diferenciaram do Trifoliata. As maiores taxas de assimila o de CO2 foram observadas por volta das 11h, com 8 mmol/m2.s, seguidas por uma diminui o, provavelmente, em vista do aumento do déficit de press o de vapor e da temperatura ambiente entre as 11 e as 14h. Após a suspens o da irriga o, a queda do potencial da água na folha foi semelhante em todas as plantas, independentemente dos porta-enxertos usados, porém, sobre `Cravo', a taxa de assimila o de CO2 decaiu mais rapidamente e recuperou-se mais vagarosamente. As plantas sobre esse porta-enxerto apresentaram, durante todo o período de deficiência hídrica, menor taxa de assimila o de CO2 que aquelas sobre Trifoliata e `Cleópatra', e semelhante ao `Troyer'. As plantas sobre Trifoliata recuperaram-se em três dias, enquanto as outras n o se recuperaram totalmente. A condutividade hidráulica foi superior para o limoeiro `Cravo' e semelhante entre os demais porta-enxertos.
Teor de água no substrato de crescimento e fotossíntese em laranjeira ?Valência?
MACHADO, EDUARDO CARUSO;MEDINA, CAMILO LáZARO;GOMES, MARA DE MENEZES DE ASSIS;
Bragantia , 1999, DOI: 10.1590/S0006-87051999000200001
Abstract: photosynthesis (a), transpiration (e), stomatal conductance (gs), leaf water potential (y), leaf relative water content (rwc), internal co2 concentration (ci) and water use efficiency (wue) have been evaluated in ′valencia′ orange trees grafted on two rootstocks exposed to substrate desiccation. daily measurements at the laboratory conditions (temperature = 27 ± 1oc, water vapor pressure 1,5 ± 0,3 kpa, and photon flux density = 700 mmol.m-2.s-1) have been made until a reached values near zero. after rehydration, the same variables above have been evaluated for additional four days. a and y values have not varied within 24% and 15% of substrate water content and for rwc ranging from 90 and 80%. however, there has been a decrease in gs along with the decline on substrate water content and rwc. it is suggested that the stomatal response is directly related to the variation in substrate water content, by root-to-shoot communication. the ratio a/e (wue) has shown a slight reduction trend as gs declined, showing that under severe stress (y < -2,7 mpa), a has reduced more than e. the increase of co2 internal concentration (ci) in y below -2,7 mpa has pointed out that, under severe stress, co2 assimilation has declined as a result of both stomatal closure and reduced photosynthesis activity. after a 12 hour-rewatering period y had recovered the initial values while a and gs had not yet reached the initial values, which have been obtained, though partially, only after a three day-rewatering period.
CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa
Habermann, Gustavo;Machado, Eduardo Caruso;Rodrigues, Jo?o Domingos;Medina, Camilo Lázaro;
Brazilian Journal of Plant Physiology , 2003, DOI: 10.1590/S1677-04202003000200003
Abstract: plants with citrus variegated chlorosis (cvc), a disease caused by the xylem-limited bacteria xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. using healthy and cvc-affected 'pêra' sweet orange plants on 'rangpur' lime rootstock, the leaf gas exchange variables were measured with an open-gas portable photosynthesis system. all plants were watered and the leaf water potential (yw) was measured by isopiestic thermocouple psychrometric technique. the net photosynthesis (a) vs. internal leaf co2 concentration (a/ci curves) was analyzed. the relative effect of stomatal resistance on photosynthesis (s%) and the estimation of carboxylation efficiency were calculated. the rates of photosynthesis and transpiration, stomatal conductance, and internal leaf co2 concentration (ci) were also measured while varying the photosynthetic photon flux density (ppfd). the s% values were approximately 30 % greater in infected plants when compared to healthy ones. the light compensation point for diseased plants was higher than in the healthy ones, and the saturation light point in plants with cvc was twofold lower. the lower yw in diseased plants favours the hypothesis of xylem occlusion, which probably caused a lower water supply to the mesophyll, thus decreasing the photosynthesis and transpiration rates. nevertheless, there was also a reduction in the photosynthetic metabolic activities, represented by lower carboxylation efficiency and photochemical disturbances that were detected in diseased plants.
Respostas da fotossíntese de três espécies de citros a fatores ambientais
Machado, Eduardo Caruso;Schmidt, Patrícia Tambelli;Medina, Camilo Lázaro;Ribeiro, Rafael Vasconcelos;
Pesquisa Agropecuária Brasileira , 2005, DOI: 10.1590/S0100-204X2005001200002
Abstract: gas exchange responses to irradiance, temperature, air vapor pressure deficit and intercellular co2 concentration were evaluated in young plants of sweet orange 'valência', tangor 'murcote' and acid lime 'tahiti' plants, under controlled conditions. maximum rates of co2 assimilation were around 9.8, 12.8 and 13.0 μmol m-2 s-1 , respectively, for 'valência', 'murcote' and 'tahiti', and these differences were related to stomatal conductance and instantaneous carboxylation efficiency. light saturation of photosynthesis was around 750 μmol m-2 s-1 for 'valência', whereas 'murcote' and 'tahiti' did not show evident light saturation, exhibiting small increases of co2 assimilation above 1,000 μmol m-2 s-1 . the co2 compensation point was 4.8, 5.8 and 5.4 pa for 'valência', 'murcote' and 'tahiti', respectively, indicating differences in photorespiration of these citrus species. leaf temperatures between 25oc and 30oc were optimum for photosynthesis of 'valência', whereas this optimum was around 30oc for 'murcote' and 'tahiti'. at temperatures above or below the optimum range, co2 assimilation was reduced by partial decrease of stomatal conductance and instantaneous carboxylation efficiency. reduced co2 assimilation rate was also caused by increasing vapor pressure deficit from 1.5 to 3.5 kpa, and this effect enhanced when temperature increased from 28oc to 35oc.
Varia??o sazonal da fotossíntese, condutancia estomática e potencial da água na folha de laranjeira 'Valência'
Machado, Eduardo Caruso;Medina, Camilo Lázaro;Gomes, Mara de Menezes de Assis;Habermann, Gustavo;
Scientia Agricola , 2002, DOI: 10.1590/S0103-90162002000100007
Abstract: seasonal variation in environmental conditions may influence gas exchange rates as well as water relations in perennial species. this work was carried out to evaluate photosynthetic rates (a), transpiration (e), stomatal conductance (g) and leaf water potential (y f ) in 'valencia' orange trees grafted on four different rootstocks. measurements were made twice a day: from 9h00 to 11h00 a.m. and from 1h00 to 3h00 p.m., during january, march and july. a and g were significantly lower and yf was significantly more negative, in the afternoon. the decrease in a may be related to the reduction in g, due to the increase in the vapor pressure deficit between the air and the leaf (vpdair-leaf ) in the afternoon, when temperatures are higher. in spite of the partial stomatal closure in the afternoon, the values for e were approximately the same as those measured in the morning, due to the increase in the vpdair-leaf . a decrease in a and g could also be noted from january to july, that is, from the hot and humid summer months, to the colder and drier winter ones. it was suggested that the decrease in a and g observed from january through march, may be related to the decrease in plant growth rates, which could have influenced the source-sink relationships, since the climatic conditions for both months were similar. the decrease in a and g showed in july, seems to be related to the decrease in both the night temperature and the growth rate of plants.
Varia o sazonal da fotossíntese, condutancia estomática e potencial da água na folha de laranjeira 'Valência'
Machado Eduardo Caruso,Medina Camilo Lázaro,Gomes Mara de Menezes de Assis,Habermann Gustavo
Scientia Agricola , 2002,
Abstract: Em espécies perenes podem ocorrer varia es nas taxas de trocas gasosas e nas rela es hídricas em fun o da varia o das condi es ambientais, durante os diferentes meses do ano. Avaliaram-se, em laranjeira ′Valência′ enxertada sobre quatro espécies de porta-enxerto, mantida sem deficiência hídrica, as taxas de fotossíntese (A) e de transpira o (E), a condutancia estomática (g) e o potencial da água na folha (psi f ), medidos nos períodos da manh (9h00 às 11h00) e da tarde (13h00 às 15h00) nos meses de janeiro, mar o e julho em Campinas - SP. As espécies de porta-enxertos n o tiveram efeitos sobre as variáveis medidas. Independente do porta-enxerto A, g e Y f foram menores no período da tarde. A queda de A deve estar relacionada com a queda de g que diminuiu em resposta ao aumento do déficit de press o de vapor entre o ar e a folha (DPVar-folha ) nos horários mais quentes do dia. Apesar de ocorrer fechamento parcial dos est matos no período da tarde E foi similar ao período da manh , devido ao aumento do DPVar-folha. Também observou-se queda em A e em g no sentido de janeiro para julho. Sugere-se que a queda em A e em g ocorrida em mar o em compara o a janeiro esteja relacionada à queda da atividade de crescimento da planta, afetando as rela es fonte-dreno, visto que as condi es ambientais nestes dois meses foram semelhantes. As quedas de A e de g observadas em julho, em rela o à janeiro e mar o, parecem estar relacionadas tanto à queda na temperatura noturna quanto à queda na atividade de crescimento.
CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa
Habermann Gustavo,Machado Eduardo Caruso,Rodrigues Jo?o Domingos,Medina Camilo Lázaro
Brazilian Journal of Plant Physiology , 2003,
Abstract: Plants with citrus variegated chlorosis (CVC), a disease caused by the xylem-limited bacteria Xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. Using healthy and CVC-affected 'Pêra' sweet orange plants on 'Rangpur' lime rootstock, the leaf gas exchange variables were measured with an open-gas portable photosynthesis system. All plants were watered and the leaf water potential (Yw) was measured by isopiestic thermocouple psychrometric technique. The net photosynthesis (A) vs. internal leaf CO2 concentration (A/Ci curves) was analyzed. The relative effect of stomatal resistance on photosynthesis (S%) and the estimation of carboxylation efficiency were calculated. The rates of photosynthesis and transpiration, stomatal conductance, and internal leaf CO2 concentration (Ci) were also measured while varying the photosynthetic photon flux density (PPFD). The S% values were approximately 30 % greater in infected plants when compared to healthy ones. The light compensation point for diseased plants was higher than in the healthy ones, and the saturation light point in plants with CVC was twofold lower. The lower Yw in diseased plants favours the hypothesis of xylem occlusion, which probably caused a lower water supply to the mesophyll, thus decreasing the photosynthesis and transpiration rates. Nevertheless, there was also a reduction in the photosynthetic metabolic activities, represented by lower carboxylation efficiency and photochemical disturbances that were detected in diseased plants.
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