Responses to UV‐B radiation in Trifolium repens L. – physiological links to plant productivity and water availability

• Published in: Plant, cell and environment cell and environment, 2003-04, Vol.26 (4), p.603-612
• Main Authors: HOFMANN, R. W., CAMPBELL, B. D., BLOOR, S. J., SWINNY, E. E., MARKHAM, K. R., RYAN, K. G., FOUNTAIN, D. W.
• Format: Article
• Language: English
• Subjects: acclimation; Adaptation to environment and cultivation conditions; Agronomy. Soil science and plant productions; Biological and medical sciences; drought; flavonoids; Fundamental and applied biological sciences. Psychology; Genetics and breeding of economic plants; high‐performance liquid chromatography; intraspecific; Plant physiology and development; quercetin; stress; ultraviolet‐B; Varietal selection. Specialized plant breeding, plant breeding aims; Water and solutes. Absorption, translocation and permeability; white clover
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1046/j.1365-3040.2003.00996.x

ABSTRACT This study used comparisons across nine populations of Trifolium repens (white clover) in conjunction with drought to examine physiological responses to ultraviolet‐B radiation (UV‐B). Plants were exposed for 12 weeks to supplementation with 13.3 kJ m−2 d−1 UV‐B, accompanied by 4 weeks of drought under controlled environmental conditions. UV‐B increased the levels of UV‐B‐absorbing compounds and of flavonol glycosides and this effect was synergistically enhanced by water stress. These changes were more pronounced for the ortho‐dihydroxylated quercetin, rather than the monohydroxylated kaempferol glycosides. UV‐B increased leaf water potential (ψL) by 16% under drought and proline levels by 23% under well‐watered conditions. The intraspecific comparisons showed that higher UV‐B‐induced levels of UV‐B‐absorbing compounds, of quercetin glycosides and of ψL were linked to lower plant productivity and to higher UV‐B tolerance under well‐watered conditions. These findings suggest that: (1) slow‐growing T. repens ecotypes adapted to other stresses have higher capacity for physiological acclimation to UV‐B; and (2) that these attributes also contribute to decreased UV‐B sensitivity under drought.