Growth, Gas Exchange, and Mineral Nutrients of Hydrangea Hybrids to Saline Water Irrigation

Authors: SUN, YOUPING - Utah State University; DOU, HAIJIE - Texas A&M University; PEREZ, CHRISTINA - Texas A&M University; NIU, GENHUA - Texas A&M University; Alexander, Lisa

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2021
Publication Date: 1/17/2022
Citation: Sun, Y., Dou, H., Perez, C., Niu, G., Alexander, L.W. 2022. Growth, Gas Exchange, and Mineral Nutrients of Hydrangea Hybrids to Saline Water Irrigation. HortScience. 57(2):319-329. https://doi.org/10.21273/HORTSCI16196-21.
DOI: https://doi.org/10.21273/HORTSCI16196-21

Interpretive Summary: Hydrangea macrophylla is one of the most economically important nursery crops in the US, with sales of Hydrangea species topping $120,000,000 in 2014. In order to expand the footprint of hydrangea production and landscape use, novel hydrangea hybrids were tested for their ability to grow in saline water. Salinity stress led to lowered visual quality of plants and stunted growth. Salinity stress also reduced the efficacy of the photosynthesis system of hydrangea plants and inhibited their photosynthesis, especially at higher salinity level. Salinity-induced nutrient imbalance was also observed, especially nitrogen, phosphorus, potassium, and iron concentrations, but didn’t cause nutrient deficiency or toxicity in this study. Two hybrids (Dichroa febrifuga ‘Yellow Wings’ x Hydrangea macrophylla ‘Nigra’ and Dichroa febrifuga ‘Yamaguchi Hardy’ x Hydrangea macrophylla ‘Hamburg’) were the most tolerant of saline water, indicating that breeding improvement is a viable method of improving salinity tolerance. Mechanisms of tolerance are under investigation and the best hybrids are being used as parents in continued breeding improvement of salinity tolerance.

Technical Abstract: Hydrangeas are popular landscape plants that are widely grown in many parts of the world. The objective of this study was to evaluate the salinity tolerance of three novel Dichroa ×Hydrangea hybrids [Dichroa febrifuga 'Yamaguchi Hardy' ×Hydrangea macrophylla 'Hamburg' (YH × Hamburg), Dichroa febrifuga 'Yellow Wings' ×Hydrangea macrophylla 'Nigra' (YW × Nigra), and Dichroa febrifuga 'Yellow Wings' ×Hydrangea macrophylla 'Oakhill' (YW × Oakhill)]. A 52-d greenhouse study was conducted by irrigating container-grown plants with nutrient solution at an electrical conductivity (EC) of 1.1 dS·m-1 (control) or saline solution at n EC of 5.0 dS·m-1 (EC5) or 10.0 dS·m-1 (EC 10). At harvest, YH × Hamburg and YW × Nigra in EC 5 and EC 10 still exhibited good quality with average visual scores greater than 4.1 (0 = dead; 5 = excellent). For YW × Oakhill, moderate foliar salt damage was observed with an average visual score of 2.9 in EC 5 and 2.2 in EC 10. Compared to control, the shoot dry weight of YH × Hamburg, YW × Nigra, and YW × Oakhill in EC 5 reduced by 35%, 35%, and 55%, respectively, whereas that in EC 10 decreased by 58%, 58%, and 67%, respectively. Elevated salinity also decreased plant height, leaf area, and leaf greenness (SPAD readings), chlorophyll fluorescence (Fv/Fm), performance index (PI), and net photosynthetic rate (Pn). All these responses might result from excess accumulation of sodium (Na+) and chloride (Cl-) ions in hydrangea leaves. In this study, compared to control, leaf Na+ concentration of YH × Hamburg, YW × Nigra, and YW × Oakhill increased 11, 36, and 14 times, respectively, in EC 5, and 31, 53, and 18 times, respectively, in EC 10. Compared to control, leaf Cl- concentration increased 4, 9, and 7 times in EC 5, and 10, 11, and 8 times in EC 10 for YH × Hamburg, YW × Nigra, and YW × Oakhill, respectively. Nitrogen (N), phosphorous (P), potassium (K+), and iron (Fe3+) concentrations decreased at elevated salinity levels but didn’t cause any nutrient deficiency. In summary, the three Dichroa x hydrangea hybrids exhibited varying salinity tolerance: YH × Hamburg and YW × Nigra were more tolerant than YW × Oakhill. Salt tolerant hydrangea hybrids should be chosen for landscape use if soil and/or irrigation water are salty.