Enhanced transpiration rate in the high pigment 1 tomato mutant and its physiological significance

Abstract

Tomato high pigment (hp) mutants represent an interesting horticultural resource due to their enhanced accumulation of carotenoids, flavonoids and vitamin C. Since hp mutants are known for their exaggerated light responses, the molecules accumulated are likely to be antioxidants, recruited to deal with light and others stresses. Further phenotypes displayed by hp mutations are reduced growth and an apparent disturbance in water loss. Here, we examined the impact of the hp1 mutation and its near isogenic line cv Micro-Tom (MT) on stomatal conductance (gs), transpiration (E), CO(2) assimilation (A) and water use efficiency (WUE). Detached hp1 leaves lost water more rapidly than control leaves, but this behaviour was reversed by exogenous abscisic acid (ABA), indicating the ability of hp1 to respond to this hormone. Although attached hp1 leaves had enhanced gs, E and A compared to control leaves, genotypic differences were lost when water was withheld. Both instantaneous leaf-level WUE and long-term whole plant WUE did not differ between hp1 and MT. Our results indicate a link between exaggerated light response and water loss in hp1, which has important implications for the use of this mutant in both basic and horticultural research.

Chromoplast-Specific Carotenoid-Associated Protein Appears to Be Important for Enhanced Accumulation of Carotenoids inhp1Tomato Fruits

“…While the gene product of ZEP converts zeaxanthin to violaxanthin, the gene product of VDE reconverts violaxanthin to zeaxanthin. The reduced expression of ZEP and the enhanced expression of VDE in hp1 appear to be in agreement with the characteristic increase in chloroplast number and size, which could be correlated to reduced ABA levels in hp1 (Carvalho et al, 2011). A similar phenotype was also observed in the ABA-deficient hp3 mutant, which has a lesion in ZEP (Galpaz et al, 2008).…”

The role of phytochromes in cadmium stress responses in tomato

“…Despite mounting evidence that phytochromes are involved in plant responses to several abiotic stresses (Carvalho et al 2011b;Auge et al 2012), none of the three phytochrome mutants assessed in the present study exhibited higher tolerance to Cd. Thus, taken together, these results indicate that phytochromes do not integrate the pathway of Cd stress response in tomato plants.…”

Biochemical and histological characterization of tomato mutants

“…4B). Although this characteristic is probably due to ABA deficiency, producing wilted plants, excessive water loss in hp1 (Carvalho et al 2011b) does not result in such characteristics. …”

“…Since an additional characteristic displayed by hp mutations is a disturbance in water loss (Galpaz et al 2008, Carvalho et al 2011b, we are currently investigating whether hp1 display an exaggerated induction of antioxidant system under stress condition, such as salt and metal stress.…”