NUCLEAR MUTATIONS AFFECTING CHLOROPLASTIC PIGMENTS OF PHOTOPERIOD-INSENSITIVE BARLEY

Three photoperiod-sensitive spring barley cultivars (Hordeum vulgare L .) and three independently derived, single-gene, nuclear mutants expre ssing photoperiod insensitivity and extremely early heading time under short daylengths were investigated for chloroplastic pigment variatio n in three environments using reverse-phase high-performance liquid ch romatography (HPLC) to account for differences in laminae colour. In a greenhouse, non-stress environment and in a full sunlight, high-tempe rature stress environment, no systematic differences were observed amo ng pigments of the mutant-parent pairs. However, under 12 h of daily l ight (600 muE m-2 sec-1) and stress temperatures (20/10-degrees-C, nig ht/day) in a growth chamber, the three mutants appeared similar pigmen t contents, but differed from the three non-chlorotic parents, which w ere similar to each other. The mutants had less chlorophyll a and b, b eta-carotene, lutein, taraxanthin, violaxanthin, and neoxanthin but mo re zeaxanthin than their parents. When shaded, the mutants became less chlorotic. How phenotypic differences for heading time and perception of day-length might be related to altered chloroplast contents remain s unclear. The single-gene mutants conferring photoperiod insensitivit y were more sensitive to photothermal stress than their photoperiod-se nsitive counterparts and as a result, their zeaxanthin content increas ed but the level of other pigments decreased.