Effect of seasonal variation and storage temperature on leaf chlorophyll fluorescence and vase life of cut roses

Abstract

Abstract Low temperature injury (LTI) of roses (Rosa hybrida L.) is difficult to assess by visual observation. Relative chlorophyll fluorescence (CF; Fv/Fm) is a non-invasive technique that provides an index of stress effects on photosystem II (PS II) activity. This instrumental technique allows determination of the photosynthetic efficiency of plant tissues containing chloroplasts, such as rose leaves. In the present study, pre- and post-storage measurements of Fv/Fm were carried out to assess LTI in ‘First Red’ and ‘Akito’ roses harvested year round. Relationships between the pre-harvest environment conditions of temperature, relative humidity and photon flux density (PFD), Fv/Fm, and, vase life duration after storage are reported. After harvest, roses were stored at 1, 5 and 10 °C for 10 days. Non-stored roses were the control treatment. Fv/Fm ratios were reduced following storage, suggesting LTI of roses. However, reductions in Fv/Fm were not closely correlated with reduced vase life duration and were seasonally dependent. Only during winter experiments was Fv/Fm of roses stored at 1 °C significantly (P ≤ 0.001) lower compared to Fv/Fm of non-stored control roses and roses stored at 5 and 10 °C. Thus, the fall of Fv/Fm was due to an interaction of growing season and storage at 1 °C. Vase lives of roses grown during winter were significantly (P ≤ 0.001) shorter compared to roses grown during summer. Length of vase life was intermediate for roses grown during autumn and spring. Because of the lack of correlation between Fv/Fm and post-storage vase life it is concluded that the CF parameter Fv/Fm is not a practical index for assessing LTI in cold-stored roses. Higher PFD and temperature in summer were positively and significantly correlated with maintenance of post-storage Fv/Fm ratios and longer vase life. It is suggested that shorter vase lives and lower post-storage Fv/Fm values after storage at 1 °C are consequences of reduced photosynthesis and smaller carbohydrate pools in winter-harvested roses.