Physiological response of juvenile hop plants to water deficit

This paper evaluates the response on the rate of photosynthesis (Pn), transpiration (E), stomatal conductance (gs) and water use efficiency (WUE) in 15 genotypes of young hop plants (19 BBCH) grown in greenhouses in the conditions of water deficit for the period of 9 days. On the 9th day, the relative content of water in the experimental plants fluctuated between 70.14-75.20%. The levels of Pn and gs evidently dropped in the monitored species as a result of the water deficit. The decrease of Pn in the experimental plants compared with the control group was largest in the Saaz Os. cl. 72 (by 77.5%), Magnum (by 73.3%) and Columbus (by 62.3%). To the contrary, the lowest Pn decrease was noted in the case of genotypes Saaz Late (by 15.7%), Vital (by 23.9%) and Premiant (by 24.2%). All genotypes except for cv. H16 showed an evident decrease of E. Judging by the highest values of WUE, the most effective water management was shown by Premiant, Vital and Saaz Late genotypes. A significant stomatal limitation of photosynthesis due to water stress was identified in the most widely used Czech cultivar, Saaz Os. cl. 72, with low values of stomatal conductance, photosynthetic rate and transpiration.