Altitude-related environmental factors shape the phenotypic characteristics and chemical profile of Rhododendron

doi:10.17520/biods.2022259

Abstract

Abstract:

Aims: Interactions between plants and the environment drive the diversity of plant phenotypes and secondary metabolites. Abiotic factors in the environment are known to vary with altitude, but it remains unclear how this variation affects plant characters and secondary metabolite composition, including whether secondary metabolites differ among different tissues and organs within a plant.

Methods: We took samples of Rhododendron virgatum, R. decorum, and R. rubiginosum from three different altitudes. We measured environmental factors at each altitude, including temperature, relative humidity, and relative light intensity. We also measured vegetative traits, characteristics of plants’ reproductive organs, and nectar features (nectar volume, sugar concentration, nectar components). We used UPLC-Qtof methods to analyze the levels and composition of secondary metabolites in the stems, leaves, petals, pollen, and nectar of populations from different altitudes.

Results: As altitude increased, the temperature, relative humidity, and relative light intensity decreased. The heights, corolla sizes, and anther volumes of the sampled plants decreased significantly, while the branch diameters and pistil and stamen lengths increased significantly. The floral nectar volume and sugar concentration at the highest altitude (altitude C) were significantly higher than at altitudes A and B, the lowest and middle altitudes. The nectar sucrose content in Rhododendron was also significantly higher at altitude C than at the lower altitudes. The secondary metabolites of the Rhododendron samples did not differ significantly at different altitudes—at every altitude, the plants were dominant in flavonoids, steroids, terpenoids, phenylpropanoids, and alkaloids, and there were significant correlations among these components. However, the secondary metabolites did vary between different organs of the plants: nectar and pollen had significantly lower levels of metabolites than branches, leaves, and petals. Additionally, PCA results showed that Rhododendron plants at altitudes A and B were relatively similar in character and metabolites. It also revealed that the flavonoid components of plants at altitude C were different from those at altitudes A and B.

Conclusion: Our results reveal a degree of adaptive variation in phenotypic characteristics and metabolite composition of Rhododendron plants at different altitudes. However, phenotypic traits vary much more than the composition and relative contents of secondary metabolites. We conclude that environmental factors present at different altitudes are much more likely to shape the external characteristics of plants than to change their internal metabolic profile.

Key words: Rhododendron, altitude, environment factors, phenotypic variation, composition and content of secondary metabolites

Renxiu Yao, Yan Chen, Xiaoqin Lü, Jianghu Wang, Fujun Yang, Xiaoyue Wang. Altitude-related environmental factors shape the phenotypic characteristics and chemical profile of Rhododendron[J]. Biodiv Sci, 2023, 31(2): 22259.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2022259

https://www.biodiversity-science.net/EN/Y2023/V31/I2/22259

Figures/Tables 7

Fig. 1 The inflorescence of Rhododendron virgatum (A), R. decorum (B), and R. rubiginosum (C) and measurement of floral characteristics of Rhododendron (D, R. decorum as example). a, Corolla length; b, Corolla width; c, Tube opening diameter; d, Floral tube length; e, Tube diameter; f, Pistil length; g, The longest stamen length; h, The shortest stamen length.

Table 1 Comparison of environmental factors (relative light intensity, temperature and relative humidity) among different altitude populations (generalized linear model, GLM). Different letters indicate significant differences in environmental factors among different altitudes. Bolded numbers indicate maximum values.

居群 Population		海拔 Elevation (m)	相对光照强度 Relative light intensity (%)	温度 Temperature (℃)	相对湿度 Relative humidity (%)
苍山 Cangshan Mountain	海拔A Altitude A	2,199.20 ± 7.96^c	0.52 ± 0.07^a	16.08 ± 0.28^b	57.17 ± 2.82^b
苍山 Cangshan Mountain	海拔B Altitude B	2,511.20 ± 10.18^b	0.40 ± 0.07^a	18.92 ± 0.20^a	60.50 ± 1.93^b
	海拔C Altitude C	2,809.00 ± 6.94^a	0.18 ± 0.04^b	12.88 ± 0.34^c	74.42 ± 2.47^a
	Wald χ2	2,593.848	14.105	234.227	28.222
	P	< 0.001	0.001	< 0.001	< 0.001
老君山 Laojun Mountain	海拔A Altitude A	3,398.20 ± 9.66^c	0.34 ± 0.04^a	12.39 ± 0.84^a	66.67 ± 2.17^a
老君山 Laojun Mountain	海拔B Altitude B	3,606.20 ± 8.80^b	0.25 ± 0.05^a	13.64 ± 1.33^a	70.33 ± 5.65^a
	海拔C Altitude C	3,796.00 ± 10.40^a	0.28 ± 0.03^a	7.73 ± 1.17^b	72.11 ± 4.19^a
	Wald χ2	851.739	3.296	11.876	0.768
	P	< 0.001	0.192	0.003	0.681

Table 2 Comparison of vegetable and reproduction organs of Rhododendron vigatum, R. decorum, R. rubiginosum at different altitudes(generalized linear model, GLM)(mean±SE). Different letters indicate significant differences in phenotypic characteristics among different altitudes of Rhododendron plants. Bolded numbers indicate the maximum values.

Fig. 2 Comparison of nectar volume (Ai) and nectar concentration (Aii) and nectar sugar content (B) of three species of Rhododendron at different altitudes (mean ± SE). Different letters indicate significant differences between different altitudes (P < 0.05).

Fig. 3 Comparison of flavonoid, steroid, terpenoid, phenylpropanoid and alkaloid contents among Rhododendron at different altitudes (mean ± SE). Different letters indicate significant differences among different organs (P < 0.05).

Table 3 The Pearson correlation analysis among Rhododendron vegetative and reproductive organs traits, the secondary materials components, altitudes and environmental factors (temperature, relative humidity and relative light intensity). In the table, the lower left value of the gray split line indicates correlation (r), and the upper right value of the gray split line indicates significance (P). If the P < 0.05, the P value will be bold, and the corresponding r value will be bold and marked as blue, light blue indicates P < 0.05, blue indicates P < 0.01, and dark blue indicates P < 0.001.

Fig. 4 Principal component analysis (PCA) of ten phenotypic characteristics and five secondary material components (flavonoid, steroid, terpenoid, phenylpropanoid and alkaloid) of Rhododendron at different altitudes

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