Efeitos da disponibilidade hídrica na fisiologia e produção de vitis vinifera l. Na região demarcada do douro
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2010
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A temática das relações hídricas na vinha e sobretudo o seu impacto na produção não
é consensual. Embora a rega seja uma prática agronómica comum em muitas zonas vitícolas
do Globo, continuam a ser levantadas questões acerca das vantagens/inconvenientes que
poderão advir da sua utilização. O presente trabalho pretende contribuir para a clarificação do
tema e contextualizá-lo nas condições particulares da Região Demarcada do Douro (RDD).
Em 2003 foi assim estabelecido um campo experimental na sub-região do Douro
Superior numa parcela de Vitis vinífera L. cv. Tinta Roriz enxertada em 1103P, com o
objectivo de avaliar o impacto de diferentes regimes hídricos no comportamento fisiológico
da videira e as suas consequências no rendimento e composição dos mostos da RDD. Os
tratamentos experimentais definidos diferiam quer na quantidade de água aplicada à vinha,
quer no período da sua aplicação: não regado (NR), regado da floração ao pintor a 50% da ET
(FP1), regado da floração ao pintor a 100% da ET (FP2), regado do pintor à maturação a 50%
da ET (PM1), regado do pintor à maturação a 100% da ET (PM2) e regado da floração à
maturação a 100% da ET (FM2).
Foram utilizados vários métodos de avaliação do estado hídrico da videira,
destacando-se pela positiva a medição da velocidade do fluxo de seiva, do potencial hídrico
foliar de base e das trocas gasosas através do IRGA. Por sua vez a estimativa do teor de
clorofilas das folhas através do SPAD e os registos da fluorescência da clorofila a não se
revelaram bons indicadores do estado hídrico da videira.
Ao longo dos três anos de trabalhos, as modalidades definidas resultaram em
diferenças significativas no teor de água no solo e consequentemente no comportamento
fisiológico, vegetativo e produtivo das videiras.
As modalidades regadas no período dos registos apresentaram taxas mais elevadas de
transpiração, condutância estomática, fotossíntese e fluxo de seiva, resultando em geral
(excepto na PM1) maiores áreas foliares e uma continuação do crescimento vegetativo após o
pintor.
Em termos de produção, as videiras não regadas registaram as menores quantidades,
sobretudo devido a um menor peso dos bagos, e apresentaram um desempenho qualitativo
inconstante, com grandes variações dos açúcares e carotenóides ao longo dos três anos,
motivadas sobretudo por efeitos de concentração pelo reduzido tamanho dos bago, e em geral
VIII
baixos teores de compostos fenólicos nas películas das uvas. A modalidade mais regada
(FM2) apresentou os rendimentos mais elevados, devido a um maior peso dos seus cachos e
bagos, mas uma menor qualidade geral, apresentando teores de açúcar, compostos fenólicos e
carotenóides baixos. O desempenho produtivo mais equilibrado resultou da manutenção das
videiras sob uma carência hídrica leve até ao pintor e média durante o período da maturação,
condições atingidas neste caso através da rega com uma dotação de 50% da ET apenas da
floração ao pintor, com vantagens quer no rendimento, quer na qualidade. Deve-se contudo
ter em conta que poderão existir diferentes opções de regime hídrico consoante os objectivos
de produção, as condições ambientais e os recursos disponíveis, não se podendo tampouco
descurar o efeito do factor “Ano”, que se verificou ter uma influência significativa na maioria
dos parâmetros de produção avaliados.
The discussion regarding vineyard’s water relations and especially its impact on production is not consensual. Although irrigation is a common agronomic practice in many wine-growing areas of the world, there are still questions about the advantages / disadvantages that may result from its use. The research presented in this thesis aims to contribute to the clarification of this issue and contextualize it in the particular conditions of the Douro Region (RDD). In 2003 an experimental site was established in the sub-region of Douro Superior, in a part of a vineyard of Vitis vinifera L. cv. Tinta Roriz grafted onto 1103P, with the aim of assessing the impact of different water regimes on the physiological behaviour of the vine and its effect in the yield and composition of the musts in RDD. The experimental treatments differed either in the amount of water supplied to the vineyard and in the timing of its application: non-irrigated (NR), irrigated from flowering to véraison with 50% of ET (FP1), irrigated from flowering to véraison with 100% of ET (FP2), irrigated from véraison to harvest with 50% of ET (PM1), irrigated from véraison to harvest with 100% of ET (PM2) and ), irrigated from flowering to harvest with 100% of ET (FM2). Different methods for assessing vine water status were used, with the best results obtained using sap flow measurements, pre-dawn leaf water potential and gas exchanges with an IRGA. SPAD’s chlorophyll content estimate on leaves and chlorophyll fluorescence were found to be unreliable indicators of vine water status. Over the three years of work, the established treatments resulted in significant differences in the water content of the soil and consequently on the vines physiological, vegetative and productive behaviours. The treatments which were being irrigated on the moment of the records lead to higher rates of transpiration, stomatal conductance, photosynthesis and sap flow, resulting in general (except for PM1) greater leaf area and a continuation of vegetative growth after véraison. Non-irrigated vines showed the lowest production, mainly due to lower berry weights, and had an inconsistent quality performance, with large variations in sugars and carotenoids contents over the three years, driven mainly by concentration effects due to the small size of the berries, and generally low levels of phenolic compounds in the grapes skins. The highest irrigation level treatment (FM2) showed the highest yields, due to the increased weight in X grapes and berries, but a lower overall quality, with low contents of sugars, phenolics and carotenoids. The most balanced production results were achieved by keeping vines under a mild water deficit until flowering and a medium water deficit during maturation, which were obtained using the irrigation with 50% of ET from flowering to véraison, showing clear advantages in both quantity and quality. One should however bear in mind that there may be different options depending on variety/cultivar, production targets, environmental conditions and available resources, not neglecting the effect of the “Year”, which was found to have a significant influence on most of the production parameters measured.
The discussion regarding vineyard’s water relations and especially its impact on production is not consensual. Although irrigation is a common agronomic practice in many wine-growing areas of the world, there are still questions about the advantages / disadvantages that may result from its use. The research presented in this thesis aims to contribute to the clarification of this issue and contextualize it in the particular conditions of the Douro Region (RDD). In 2003 an experimental site was established in the sub-region of Douro Superior, in a part of a vineyard of Vitis vinifera L. cv. Tinta Roriz grafted onto 1103P, with the aim of assessing the impact of different water regimes on the physiological behaviour of the vine and its effect in the yield and composition of the musts in RDD. The experimental treatments differed either in the amount of water supplied to the vineyard and in the timing of its application: non-irrigated (NR), irrigated from flowering to véraison with 50% of ET (FP1), irrigated from flowering to véraison with 100% of ET (FP2), irrigated from véraison to harvest with 50% of ET (PM1), irrigated from véraison to harvest with 100% of ET (PM2) and ), irrigated from flowering to harvest with 100% of ET (FM2). Different methods for assessing vine water status were used, with the best results obtained using sap flow measurements, pre-dawn leaf water potential and gas exchanges with an IRGA. SPAD’s chlorophyll content estimate on leaves and chlorophyll fluorescence were found to be unreliable indicators of vine water status. Over the three years of work, the established treatments resulted in significant differences in the water content of the soil and consequently on the vines physiological, vegetative and productive behaviours. The treatments which were being irrigated on the moment of the records lead to higher rates of transpiration, stomatal conductance, photosynthesis and sap flow, resulting in general (except for PM1) greater leaf area and a continuation of vegetative growth after véraison. Non-irrigated vines showed the lowest production, mainly due to lower berry weights, and had an inconsistent quality performance, with large variations in sugars and carotenoids contents over the three years, driven mainly by concentration effects due to the small size of the berries, and generally low levels of phenolic compounds in the grapes skins. The highest irrigation level treatment (FM2) showed the highest yields, due to the increased weight in X grapes and berries, but a lower overall quality, with low contents of sugars, phenolics and carotenoids. The most balanced production results were achieved by keeping vines under a mild water deficit until flowering and a medium water deficit during maturation, which were obtained using the irrigation with 50% of ET from flowering to véraison, showing clear advantages in both quantity and quality. One should however bear in mind that there may be different options depending on variety/cultivar, production targets, environmental conditions and available resources, not neglecting the effect of the “Year”, which was found to have a significant influence on most of the production parameters measured.
Descrição
Tese de Doutoramento em Ciências Agronómicas
Palavras-chave
Vitis Vinifera l. , Fisiologia Vegetal