The Effect of Water Deficit On Gas Exchange of Juvenile Hop Plants (Humulus lupulus L.).

The hop plants grow on area 53335 ha (year 2008) in Czech Republic. The hop plants grow in three region, two areas are in Bohemia (Saaz – 3 953 ha and Auscha – 663 ha) and one area is Moravia (Tirchitz – 719 ha) in the Czech Republic. Hop plants are very demanding as concerns sufficient amount of water, and therefore the aim of the experiments was to monitor the impact of water deficit on the exchange of gases in the juvenile hop plants. The impact of water deficit was observed in controlled greenhouse conditions where the plants of Žatecký poloraný èerveòák (SAAZ)“Osvaldùv klon 72” were cultivated in 15 l containers in two groups – the control group and the stressed group. In the stressed group, irrigation was interrupted for a period of nine days and then seven-day dehydration followed. The control group was irrigated to full saturation. In the hop plants, the photosynthesis rate, the transpiration rate and the stomatal conductivity were measured gasometrically by means of the LCpro+ instrument. It is apparent from the obtained results that after irrigation is interrupted, the levels of stomatal conductivity, transpiration rate and photosynthesis rate significantly decrease. After nine days of stress, the stomatal conductivity reached almost a zero level and the photosynthesis rate was 0.07 mmol CO₂.m^-2.s^-1 and the transpiration rate was 0.08 mol H₂O.m^-2.s^-1. When irrigation was resumed, the stomatal conductivity, transpiration rate and photosynthesis rate increased. At the end of the experiment, the photosynthesis rate reached 62 % of the pre-stress level and the stomatal conductivity and transpiration rate reached 38 % of the pre-stress level.

Supported by the MEYS of the Czech Republic, Project No. 6046070901.