Abstract
While nectaries are commonly found in flowers, some
plants also form extrafloral nectaries on stems or leaves. For
the first time in the family Brassicaceae, here we report
extrafloral nectaries in Brassica juncea. The extrafloral
nectar (EFN) was secreted from previously amorphic sites
on stems, flowering stalks and leaf axils from the onset of
flowering until silique formation. Transverse sections at the
point of nectar secretion revealed a pocket-like structure
whose opening was surrounded by modified stomatal guard
cells. The EFN droplets were viscous and up to 50% of the
total weight was sugars, 97% of which was sucrose in the
five varieties of B. juncea examined. Threonine, glutamine,
arginine and glutamate were the most abundant amino
acids. EFN droplets also contained glucosinolates, mainly
gluconapin and sinigrin. Nectar secretion was increased
when the plants were damaged by chewing above- and
belowground herbivores and sap-sucking aphids. Parasitoids
of each herbivore species were tested for their preference,
of which three parasitoids preferred EFN and sucrose
solutions over water. Moreover, the survival and fecundity
of parasitoids were positively affected by feeding on EFN.
We conclude that EFN production in B. juncea may
contribute to the indirect defence of this plant species.
| Original language | English |
|---|---|
| Pages (from-to) | 528-541 |
| Journal | Plant Cell and Environment |
| Volume | 36 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2013 |
Keywords
- international