These Common Daisies were found at Pewsey Downs, Wiltshire this week. Daises were growing everywhere however, a very small number in just a couple of areas, had this red marking in the centre - to a lesser or greater degree.
Any help with an explanation would be appreciated - some kind of rust? Have they been galled?
I don't think the redness of the tips of the disc florets is a sign of a pathogen of any kind at work. It is much more likely to be a concentration of the pigment, anthocyanin. Plants utilise anthocyanin as a form of sun-block to protect against UV damage and to prevent photoinhibition or high light stress.
The pigment is accumulated in areas where there is active cell division and growth such as new leaves and, as in this case, flower buds to protect the developing tissues. Once the leaves and flowers buds are mature the anthocyanin will be broken down by the plant again. Mature plants which are water and/or heat/light stressed will also produce anthocyanin to protect their tissues.
These inner florets of the daisy are still maturing so the anthocyanin may be helping to protect them especially if the weather went from overcast to very sunny in a matter of days.
Hope that helps,
That's really interesting Jen, thank you very much.
I assume this is a common occurence then even though it was the first time I'd noticed it.
So the anthocyanin presents itself as these red markings on the buds, in this case, & disappears once it has broken down & its job is done?
Is this the same process that makes Daisy petal tips sometimes turn pink?
It is the same pigment, but the degree to which daisy petals go pink is probably a different situation and primarily to do with the genetics of that plant. I would imagine that the anthocyanin does play a role in protecting the petals from sun damage too however it is a secondary one as the outer petals becoming damaged will not adversely affect the ability ot the plant to reproduce, whereas the small inner florets being damaged would, as these are the fertile, seed producing, flowers. There is quite a marked variation in the pinkness of the petals in the three images you uploaded, the flower with the most pigment in the centre of the flower has the whitest petals...
Plants will break down anthocyanin if it becomes less stressed e.g gains an adequate supply to water again to allow it to photosynthesis normally once more and/or it no longer requires the pigment to protect delicate tissues from excessive UV.