State evaluation of some Hydrangea macrophylla (Thunb.) varieties after winter hardiness in the agrometeorological conditions of central Russia

Hydrangea macrophylla (Thunb.) Ser. is one of the most popular ornamental crops, used in landscape design. This article represents the study of the variety resistance of species and influence their of climatic change. In that sense the effective technology of plant shelter for the winter hardiness can be considered as a successful important factor for the promotion of this crop in northern area. Wherefore we consider in a comparative analysis of H. macrophylla varieties Forever & Ever Blue and Peppermint, which we carried out after winter hardiness in the conditions of central Russia. The most reliable and proven way to shelter for winter of hydrangea is the shelter of lutrasil, which contributed to an increase in the viability of shoots and the amount awakened buds, and also provided the better growth of shoots during the month. The highest percentage of overwintered shoots (77,8%), the amount of vegetative and generative buds (19,3±1,3 сm и 9,6±0,7 сm., respectively) and the total growth of shoots in spring (10,2 cm) were characteristic for variety Forever & Ever Blue for using lutrasil as a shelter. Keywords: HYDRANGEA MACROPHYLLA, VARIETIES, WINTER HARDINESS, FROST RESISTANCE, VIABILITY, SHELTER

Iron Supplement-Enhanced Growth and Development of Hydrangea macrophylla In Vitro under Normal and High pH

Hydrangea macrophylla is a popular perennial ornamental shrub commercially grown as potted plants, landscape plants, and cut flowers. In the process of reproduction and production of ornamental plants, the absorption of nutrients directly determines the value of the ornamental plants. Hydrangea macrophylla is very sensitive to the content and absorption of the micronutrient iron (Fe) that affects growth of its shoots. However, the physiological activity of Fe as affected by deficiency or supplementation is unknown. This work aimed at preliminary exploring the relationship between Fe and photosynthesis, and also to find the most favorable iron source and level of pH for the growth of H. macrophylla. Two Fe sources, non-chelated iron sulfate (FeSO4) and iron ethylenediaminetetraacetic acid (Fe-EDTA), were supplemented to the multipurpose medium with a final Fe concentration of 2.78 mg·L−1. The medium without any Fe supplementation was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70, before autoclaving. The experiment was conducted in a culture room for 60 days with 25/18 °C day and night temperatures, and a 16-hour photoperiod provided at a light intensity of 50 mmol·m−2·s−1 photosynthetic photon flux density (PPFD) from white light-emitting diodes. Supplementary Fe increased the tissue Fe content, and leaves were greener with the medium pH of 4.70, regardless of the Fe source. Compared to the control, the number of leaves for plantlets treated with FeSO4 and Fe-EDTA were 2.0 and 1.5 times greater, respectively. The chlorophyll, macronutrient, and micronutrient contents were the greatest with Fe-EDTA at pH 4.70. Furthermore, the Fe in the leaf affected the photosynthesis by regulating stomata development, pigment content, and antioxidant system, and also by adjusting the expression of genes related to Fe absorption, transport, and redistribution. Supplementation of Fe in a form chelated with EDTA along with a medium pH of 4.70 was found to be the best for the growth and development of H. macrophylla plantlets cultured in vitro.

Influence of Solution Combination for Postharvest Treatment Stage on Vase Life of Cut Hydrangea Flowers (Hydrangea macrophylla cv. ‘Verena’)

Vase life is one of the most important factors that determines the marketability of cut flowers and is greatly affected by the water balance. The vase life of cut hydrangea flowers varies greatly depending on the postharvest solution management. Therefore, this study investigated the vase life of freshly harvested hydrangea (Hydrangea macrophylla ‘Verena’) according to the three types of preservative solutions (tap water (TW), 1% Chrysal Professional Ⅲ (CPⅢ), 2% sucrose + 250 mg/L 8-hydroxquinoline + 100 mg/L citric acid (SHQC)) and the combination solutions (pretreatment; TW, 0.1% Chrysal RVB (RVB), Floralife Quick Dip (FQ), transport; TW, CPⅢ, Floralife Clear (FC), preservative; CPⅢ, FC) for each distribution stage (pretreatment–transport–consumer). In the preservative comparison experiment, compared with the control, SHQC and CPⅢ significantly increased the vase life in 2019 (0.7 days, 3.4 days) and 2020 (1.4 days, 3.1 days), respectively. In the comparative experiment, by solution combination, the group (RVB, FQ) using the pretreatment significantly extended the vase life by 5.9 days and 4.6 days compared with the TW. These results confirm the importance of preservative solutions and pretreatment, suggesting that appropriate pretreatment and preservatives should be used to improve the marketability of cut hydrangea flowers.

Comparison of Vase Life on Treatments with Combinations of Postharvest Solutions of Cut Hydrangea Flowers (Hydrangea macrophylla cv. ‘Verena’) in Distribution Stage

Vase life is one of the most important factors that determine the marketability of cut flowers and is greatly affected by the water balance. In recent years, cut hydrangea flowers are increasingly consumed as decorations for various events. However, the vase life of cut hydrangea flowers varies greatly depending on the postharvest solution management. Therefore, this study investigated the vase life, solution uptake, water balance, and relative fresh weight of freshly harvested hydrangea (Hydrangea macrophylla ‘Verena’) according to the three types of holding solutions (tap water, 1% chrysal professional Ⅲ (CPⅢ), 2% sucrose + 250 mg/L 8-hydroxquinoline + 100 mg/L citric acid (SHQC)) and the combination solutions (pretreatment; tap water, 0.1% chrysal RVB (RVB), floralife quickdip (FQ), transport; tap water, CPⅢ, floralife clear (FC), preservatives; CPⅢ, FC) for each distribution stage (pretreatment-transport-consumer). In the preservative comparison experiment, compared with the control, CPⅢ treatment and SHQC treatment significantly increased the vase life in 2019 (0.7 days, 3.4 days) and 2020 (1.4 days, 3.1 days), respectively. In the comparative experiment by solution combination, the group (RVB, FQ) using the pretreatment significantly extended the vase life by 4.6 days and 5.9 days compared to the tap water treatment. It was also determined that the same treatment increased overall solution uptake, maintained water balance longer, and increased relative fresh weight. These results confirm the importance of holding solutions and pretreatments, suggesting that appropriate pretreatments and preservatives should be used to improve the marketability of cut hydrangea flowers.

Organic antioxidant dynamics in Hydrangea macrophylla Ser. leaves in humid subtropics of Russia

Subtropical ornamental crops have been cultivated and studied in the humid subtropics of Russia for over a century. Nevertheless, a comprehensive evidence on their adaptation and stress is rather scarce for the region. The climatic conditions in Russian humid subtropics may occur extreme to introduced plants, which warrants research into their adaptive reactions to soil aridity and summer temperatures over +30 C°. Given the situation, understanding the mechanisms of main stressor-adaptive responses is relevant in ornamental crops, including Hydrangea macrophylla Ser. Gas chromatography-mass spectrometry was employed to study ethanol leaf extracts in various-hardiness Hydrangea macrophylla Ser. cultivars, relatively hardy (Draps Wonder, Admiration, Altona), medium-hardy (Souer Theresa) and susceptible (Harlequin, Madame Faustin) forms. Eleven endogenous organic compounds have been identified, of most interest being antioxidants and stress-protectants, including diarylethylene aromatic hydrocarbons (2,4’-dihydroxystilbene), squalene and phytosterines (y/p-sitosterol). The organic leaf content changed in response to hydrothermal stress in H. macrophylla, with a maximal concentration (2,4’-dihydroxystilbene 14.0, sitosterol 5.7 %) observed in favourable hydrothermal conditions of April, and minimal — in the first August decade (8.5 and 1.7 %, respectively). Meanwhile, the relatively hardy Draps Wonder, Admiration and Altona varieties possessed the highest organic content of 2,4’-dihydroxystilbene (18.4, 21.5, 21.6 %) and y/p-sitosterol (5.7, 7.5, 6.0 %) both in optimal and stressing times. The lowest synthesis in the periods was observed in the unstable H. macrophylla varieties, Madame Faustin (6.9 and 1.1 %) and Harlequin (7.6 and 1.4 %).

Dihydroisocoumarin Content and Phenotyping of Hydrangea macrophylla subsp. serrata Cultivars under Different Shading Regimes

Hortensias (Hydrangea macrophylla L.) are well known as ornamental plants with their impressive flowers. Besides being an ornamental plant, some hortensia species contain constituents of nutritional and pharmaceutical interest. In this context, H. macrophylla subsp. serrata contains dihydroisocoumarins (DHCs), in particular hydrangenol (HG) and phyllodulcin (PD), which determine produce quality. For the successful cultivation of H. macrophylla subsp. serrata, shading may be required. The response of H. macrophylla subsp. serrata as a source for DHCs was investigated in two growing seasons using three different cultivars (‘Amagi Amacha’, ‘Oamacha’ and ‘Odoriko Amacha’) under three different light conditions: no shade (100% photosynthetic active radiation, PAR), partial (72% PAR) and full shading (36% PAR). The shading regimes had no significant effect on dihydroisocoumarin content in leaf dry matter in each single cultivar. However, ‘Amagi Amacha’ and ‘Oamacha’ yielded significantly higher PD content in comparison to ‘Odoriko Amacha’, which showed, in contrast, the significantly highest HG content. The total biomass was not significantly affected by the shading regime, but slightly higher biomass was observed under partially shaded and full-shade conditions. Hyperspectral vegetation indices (VIs) and color measurements indicate less vital plants under no shade conditions. While lighting is an important growth factor for hortensia production, DHC is cultivar dependent.

In Vitro Induction and Characterization of Polyploid Hydrangea macrophylla and H. serrata

Hydrangea macrophylla (Thunb.) Ser. and H. serrata (Thunb.) Ser. are popular and commercially important landscape and floriculture crops. Although both species are typically diploid, induced polyploids often exhibit horticulturally valuable traits. Procedures for inducing polyploidy vary by species and often have low or inconsistent efficacy. In this study, oryzalin and nitrotyrosine were investigated as in vitro mitotic inhibitors for inducing polyploidy in H. macrophylla ‘Robert’ and H. serrata ‘MAK20’. First, shoot apices of ‘MAK20’ were treated with 15 μm oryzalin for 0, 2, 4, 6, or 8 days, and the ploidy of shoots was determined after 8 weeks. A regression analysis showed that the proportion of polyploids (tetraploid plus mixoploid shoots) increased with the exposure duration. During a follow-up experiment, ‘MAK20’ and ‘Robert’ were treated with oryzalin (0 or 15 μm) and nitrotyrosine (0, 25, 50, and 100 µm for ‘MAK20’ and 0, 12.5, 25, 50, and 100 µm for ‘Robert’) in a factorial treatment arrangement. Oryzalin, nitrotyrosine, and their interaction influenced polyploid frequency for ‘Robert’, whereby the combination of oryzalin (15 μm) and nitrotyrosine (50 μm) resulted in the highest polyploid induction of 50%. Oryzalin influenced polyploid frequency for ‘MAK20’ ( = 30.4%), but not nitrotyrosine or the interaction between nitrotyrosine and oryzalin. Morphology and pollen germination of these autotetraploid ‘Robert’, ‘MAK20’, and previously developed autotetraploid H. macrophylla ‘David Ramsey’ plants were compared with their diploid counterparts 1 year after plants were moved ex vitro. Compared with diploids, tetraploid hydrangeas had larger leaves, thicker stems, lower leaf area/fresh weight ratios, and longer internodes. Although all tetraploids exhibited fewer inflorescences per plant, both H. macrophylla cultivars had larger inflorescence diameters and ‘David Ramsey’ had a greater number of showy florets (sterile florets with enlarged, decorative sepals) per inflorescence. Sepal colors were compared using International Commission on Illumination L*a*b* color space. Tetraploid ‘MAK20’ had lower L* values (darker sepals), and tetraploid ‘Robert’ and ‘MAK20’ both had higher a* values (redder sepals). Pollen germination rates were greatly reduced in all tetraploid lines, but they retained some viability. These results provide an effective protocol for in vitro polyploid induction of Hydrangea sp. and documented certain desirable traits associated with tetraploid phenotypes.