PHYSIOLOGICAL CHARACTERIZATION OF EXAGGERATED-PHOTORESPONSE MUTANTS OF TOMATO

Four monogenic mutants in tomato (Lycopersicon esculentum Mill.), i.e. three recessive mutations, high-pigment-1 (hp-l), high-pigment-2 (hp- 2), and atroviolacea (atv), and one dominant mutation, Intense pigment ation (Ip), were used in this study. These mutants all show exaggerate d photoresponses during deetiolation and seedlings having shorter hypo cotyls and higher anthocyanin levels. The hp-1 and hp-2 have higher ch lorophyll levels in immature fruit, giving them a dark green colour. S pectrophotometrical and immunological analyses of phytochrome A and ph ytochrome B revealed no differences between the mutants and the wild t ypes (WTs), suggesting that the mutants are not photoreceptor mutants. Both hp-1 and hp-2 accumulate high levels of anthocyanin in continuou s blue (B) and red (R) broad-band light. In contrast, atv has a WT lev el of anthocyanin in B and an exaggerated response ill R. The It, muta nt has the opposite response: a WT level of anthocyanin in R and an ex aggerated response in B. In B and R pretreatment studies, all mutants show an enhanced R/far-red light (FR)-reversible response compared wit h WT, but the Ip mutant shows a preferentially enhanced response in B. The hp-1 mutant exhibits a strong amplification of both the low fluen ce rate response and high irradiance response components of anthocyani n biosynthesis in red light. The atv mutant shows the strongest amplif ication of the HIR component. The Ip mutant exhibits an exaggerated an thocyanin response in B. All four mutants exhibit a normal elongation response to supplementary FR during the daily photoperiod.