On the role of flavonoids in the integrated mechanisms of response of Ligustrum vulgare and Phillyrea latifolia to high solar radiation

• The role of flavonoids in mechanisms of acclimation to high solar radiation was analysed in Ligustrum vulgare and Phillyrea latifolia, two Mediterranean shrubs that have the same flavonoid composition but differ strikingly in their leaf morphoanatomical traits. • In plants exposed to 12 or 100% solar radiation, measurements were made for surface morphology and leaf anatomy; optical properties, photosynthetic pigments, and photosystem ll efficiency; antioxidant enzymes, lipid peroxidation and phenylalanine ammonia lyase; synthesis of hydroxycinnamates and flavonoids; and the tissue-specific distribution of flavonoid aglycones and ortho-dihydroxylated B-ring flavonoid glycosides. • A denser indumentum of glandular trichomes, coupled with both a thicker cuticle and a larger amount of cuticular flavonoids, allowed P. latifolia to prevent highly damaging solar wavelengths from reaching sensitive targets to a greater degree than L. vulgare. Antioxidant enzymes in P. latifolia were also more effective in countering light-induced oxidative load than those in L. vulgare. Consistently, light-induced accumulation of flavonoids in L. vulgare, particularly ortho-dihydroxylated flavonoids in the leaf mesophyll, greatly exceeded that in P. latifolia. • We conclude that the accumulation of flavonoid glycosides associated with high solar radiation-induced oxidative stress and, hence, biosynthesis of flavonoids appear to be unrelated to 'tolerance' to high solar radiation in the species examined

Investigation on occurrence and ultrastructure of the proteinaceous nuclear inclusions (PNIs) in the Bignoniaceæ

SUMMARYThis paper analyzes the occurrence and distribution of Proteinaceous Nuclear Inclusions (PNIs) in the family Bignoniaceae. In 52 out of 70 examined species (corresponding to 74.2%) nuclear inclusions with lamellar substructure are observed. An additional crystalline body, derived by packing of lamellar inclusion subunits during cell development, is reported in several taxa. PNIs are recorded in all studied tribes, but with different distribution. Most Tecomeae and all taxa of Crescentieae, Coleeae, Oroxyleae, Eccremocarpeae and Schlegeliae show PNIs. In most Bignonieae they are lacking. The occurrence of PNIs in two tribes considered to be the oldest groups of Bignoniaceae and related to the ancestral stock of Tubiflorae, Tecomeae and Oroxyleae, support their presence as an ancestral trait. Although systematic conclusions in Bignoniaceae cannot to be made in consequence of the great structural homogeneity of PNIs, the relationships between occurrence data and geographic distribution patterns, are discussed. Fin..