ObjectivesHydrangea macrophylla is one of the most important ornamental plants. The present paper aimed to study effects of Al2(SO4)3 on flower colour of Hydrangea macrophylla.
MethodsHydrangea macrophylla cultivar ‘mama blue’ was selected as material, and a pot experiment was conducted by setting up two Al2(SO4)3 concentration levels, 2‰ and 4‰. Al2(SO4)3 was added into the growth media when the flower bud was about 1 cm length, and citrate buffer (pH 6.0) was added in control plants. The composition and concentrations of anthocyanins were determined by HPLC and mass spectrometry, ion concentrations were measured by ICP-AES, and expression of Al3+ transport related genes was clarified by qRT-PCR.
Results The petal colour changed from pink to purple and blue-purple after 21 d by the 2‰ and 4‰ Al2(SO4)3 application, respectively. Twelve kinds of anthocyanins, such as delphinidin 3-glucoside, were detected in the petal. The Al2(SO4)3 treatments increased the anthocyanins contents, especially the delphinidinderivatives contents. The delphinidinderivatives contents in petals were increased from 5159.9 μg/g FW in control plants to 24681.2 μg/g FW and 30485.7 μg/g FW in 2‰ and 4‰Al2(SO4)3 treated plants, respectively. The increase of delphinidin derivatives contents was due to the enhancement of delphinidin 3-glucoside and delphinidin 3-pentose-5-glucoside.The delphinidin 3-glucoside contents in petals were increased from 4679.2 μg/g FW in control plants to 23610.0 μg/g FW and 29129.7μg/g FW in 2‰ and 4‰ Al2(SO4)3 treated plants, respectively, and the contents of delphinidin 3-pentose-5-glucoside in petals were increased from 142.3 μg/g FW in control plants to 805.6 μg/g FW and 1114.9 μg/g FW in 2‰ and 4‰ Al2(SO4)3 treated plants, respectively. And the Al3+ contents in petals were increased from 2.24 μg/g FW in control plants to 5.12 μg/g FW and 11.83 μg/g FW in 2‰ and 4‰ Al2(SO4)3 treated plants, respectively. Accordingly, the gene expression of vacuolar Al transporter (VALT) and plasma membrane Al transporter (PALT) were increased significantly (P < 0.05) by the Al2(SO4)3 application. Compared with control plants, the PALT expression levels were increased by 88.5% and 148.2% in 2‰ and 4‰ Al2(SO4)3 treated plants, respectively, and the VALT expression levels were increased by 74.8% and 135.7%.
ConclusionsOur results suggested that Al2(SO4)3 application induced the gene expression of VALT and PALT, enhanced the accumulation of Al3+, increased the delphinidinderivatives contents, and thus changed the flower colour from pink to purple and blue-purple.
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