By characterising the patterns of response to UV radiation in terms of the photoprotection and UV-screening of plants across a diversity of species, we hope to better understand how and why these response evolved and what environmental cues underpin their induction.
We spent the last weeks of May the at 2100 m a.s.l. in the Alps at the Jardin Botanique du Lautaret measuring solar radiation and the responses of plants to it. I did some measurements of solar radiation but spent most of the time photographing plants and lichens to record their optical properties in the ultraviolet-A, visible and near-infrared regions of the spectrum.
Several of the photographs I took of site, crew, plants and lichens available at my photography website in a post published earlier today (as I have the server set up for easy creation of galleries). These photographs are stored at Flickr.
Faba bean’s wild ancestors grew in the Mediterranean region. Domestication took place about 10000 BC, most likely in what is currently Northern Israel. The wild ancestor grew in this region. Consequently, faba bean is one of the oldest or “founder” crops cultivated from the very start of agriculture. Nowadays it is an important source of protein and widely grown in cool and temperate regions. From the Mediterranean region it spread to other regions including the Americas and Northern Europe.
Faba beans have been under cultivation at high elevation in equatorial South America since the times of the Spanish conquest, i.e. for a few hundred years. Faba bean spread to the North much earlier, as their is evidence for its cultivation in Sweden already during the Stone Age.
In these two regions environmental conditions during the growing season are very different with respect to exposure to ultraviolet radiation, while temperatures are similar as the effects of latitude and elevation are opposite. Comparing accessions from these two regions should shed light on adaptive traits conferring tolerance to UV exposure. Our first publication from this line of research has been published on-line in the journal Photochemical and Photobiological Sciences and will be part of a special issue, as well as included in Yan Yan’s thesis.
The most obvious difference is in the flavonoid composition, in particular the level of glycosilation of Kamferols.
Blue light and UV radiation shape a plant’s morphology and development, but accession-dependent responses under natural conditions are unclear. Here we tested the hypothesis that two faba bean (Vicia faba L.) accessions adapted to different latitudes and altitudes vary in their responses to solar blue and UV light. We measured growth, physiological traits, phenolic profiles and expression of associated genes in a factorial experiment combining two accessions (Aurora, a Swedish cultivar adapted to high latitude and low altitude; ILB938, from the Andean region of Colombia and Ecuador, adapted to low latitude and high altitude) and four filter treatments created with plastic sheets: 1. transparent as control; 2. attenuated short UV (290–350 nm); 3. attenuated UV (290–400 nm); 4. attenuated blue and UV light. In both accessions, the exclusion of blue and UV light increased plant height and leaf area, and decreased transcript abundance of ELONGATED HYPOCOTYL 5 (HY5) and TYROSINE AMINOTRANSFERASE 3 (TAT3). Blue light and short UV induced the accumulation of epidermal and whole-leaf flavonoids, mainly quercetins, and the responses in the two accessions were through different glycosides. Filter treatments did not affect kaempferol concentration, but there were more tri-glycosides in Aurora and di-glycosides in ILB938. Furthermore, fewer quercetin glycosides were identified in ILB938. The transcript abundance was consistently higher in Aurora than in ILB938 for all seven investigated genes: HY5, TAT3, CHALCONE SYNTHASE (CHS), CHALCONE ISOMERASE (CHI), DON-GLUCOSYLTRANSFERASE 1 (DOGT1), ABA INSENSITIVE 2 (ABI2), AUXIN-INDUCIBLE 2–27 (IAA5). The two largest differences in transcript abundance between the two accessions across treatments were 132-fold in CHS and 30-fold in DOGT1 which may explain the accession-dependent glycosylation patterns. Our findings suggest that agronomic selection for adaptation to high altitude may favour phenotypes with particular adaptations to the light environment, including solar UV and blue light.