Photosynthetic parameters and cut-flower yield of rose ‘Eurored’ (H.T.) are adversely affected by mild water stress irrespective of substrate composition

Abstract

The aim of the present study was to provide a better insight into the adaptive processes within rose plants ‘Eurored’ (Hybid Tea), grown in soilless cultivation, when exposed to water deficit. Rose plants were grown in three different substrates (perlite, pine bark–almond shells 1:1, and perlite–pumice 1:1) and under two water regimes (100 and 67% of the irrigation needs). Photosynthetic parameters, water relations, leaf chlorophyll content, chlorophyll fluorescence and cut-flower production were determined. Mild water stress caused: (a) a negative effect on photosynthetic rate and stomatal conductance but no reduction in intercellular CO 2, (b) a decline in leaf chlorophyll and chlorophyll fluorescence, (c) a decrease in transpiration rate, leaf water potential (LWP) and relative water content (RWC) but an increase in water use efficiency (WUE), (d) a reduction in total production of flower stems, though the number of extra-quality flower stems was not affected. Substrates did not affect the physiological, biochemical or growth parameters. The reduction in photosynthetic rate without being followed by any change in intercellular CO 2 concentration indicates, in addition to stomatal, the involvement of non-stomatal factors in the process, leading to a limited supply of metabolic energy and therefore to plant growth restriction.