The Contribution of Volatile Organic Compounds (VOCs) Emitted by Petals and Pollen to the Scent of Garden Roses

Flower scent is an important trait of ornamental roses and has been an important character in the selection processes. In the present study, the composition of the volatile organic compounds (VOCs) emitted by both petals and pollen of 21 garden roses (Chinensis, Climber, English rose, Floribunda, Hybrid Tea, Multiflora, Damascena, Musk rose, Polyantha, Rugosa and Shrub) was investigated through the GC-MS Static Headspace method. A total of 19 different VOCs were detected, and for each identified compound, an odorant description was included. In petals, the most common VOCs were 2-phenylethanol, methyl eugenol, and hexanal, present in 95%, 86% and 86% of garden roses, respectively. While, in pollen were methyl eugenol, methyl-1-butanol, and hexanal (present in 100%, 95%, and 90% of the genotypes, respectively), even if in lower content. The comparison between the petals and pollen profile shown that, even with less quantity, the main compounds characterizing the scent of the studied roses are present both in the petals and in the pollen (19 and 17 compounds, respectively), with different magnitude. Overall, the content of VOCs emitted by petals was more than five times higher than that produced by pollen. Different and characteristic VOCs profiles were emitted by petals and pollen of the studied garden roses

Cold treatment breaks dormancy but jeopardizes flower quality in Camellia japonica L.

Camellia japonica L. is an evergreen shrub whose cultivars are of great ornamental value. In autumn, after flower bud differentiation, dormancy is initiated. As in many other spring flowering woody ornamentals, winter low temperatures promote dormancy release of both flower and vegetative buds. However, warm spells during late autumn and winter can lead to unfulfilled chilling requirements leading to erratic and delayed flowering. We hypothesized that storing plants at no light and low temperature could favor dormancy breaking and lead to early and synchronized flowering in response to forcing conditions in C. japonica ‘Nuccio’s Pearl’. Plants with fully developed floral primordia were stored at dark, 7∘C, and RH > 90% for up to 8 weeks. To monitor endodormancy release during the storage, we evaluated the content of abscisic acid (ABA) in flower buds and the expression profiles of five putative genes related to dormancy and cold acclimation metabolism in leaves and flower buds. In addition, the expression of four anthocyanin biosynthesis pathway genes was profiled in flower buds to assess the effect of the treatment on flower pigment biosynthesis. At 0, 4, 6, and 8 weeks of cold treatment, 10 plants were transferred to the greenhouse and forced to flower. Forced plant flower qualities and growth were observed. The ABA content and the expression profiles of two dormancy-related genes (CjARP and CjDEH) suggested that dormancy breaking occurred after 6–8 weeks of cold treatment. Overall, plants treated for 6–8 weeks showed earlier vegetative sprouting, enhanced, and homogeneous flowering with reduced forcing time. Prolonged cold treatments also reduced flower size and longevity, anthocyanin content, and pigment biosynthesis-related gene transcripts. In conclusion, the cold treatment had a promotive effect on dormancy breaking but caused severe drawbacks on flower quality