Effect of ontogeny, heterophylly and leaf position on the gas exchange of the hop plant

Abstract

This paper evaluates the influence of ontogeny and the position of bine and offshoot leaves on the rate of photosynthesis (Pn), transpiration (E) and stomatal conductance (gs) in hop plants. In the ontogeny influencing Pn, E and gs among hops. The highest Pn was measured in phase 81-89 BBCH and E and gs in phase 61-69 BBCH. The Pn increased over the course of ontogeny from the 1st to 3rd level of the hop plants. From the 61 BBCH phase, the leaves of the first and second level achieved a photosynthetic maturity and Pn value no longer increased. The third-level leaves achieved photosynthetic maturity from the 81 BBCH phase. Higher E was measured in the upper parts of the hop plant. Pn and E were higher in the bine leaves in the third level of the hop plant over the entire course of the vegetation period. In the first and second level of the hop plant, higher values of Pn were measured in the offshoot leaves. Differences in gs were not noteworthy among the leaf types. Results show that a significant factor affecting the differences in Pn and E in hops is the age of the leaves.

Keywords

• humulus lupulus l.
• rate of photosynthesis
• bine leaves
• offshoot leaves
• ontogenetic development