Impact of Suboptimal Temperature on Growth, Photosynthesis, Leaf Pigments and Carbohydrates of Domestic and High-altitude Wild Lycopersicon Species

Abstract

The impact of near-optimal (25/20 degrees C) and suboptimal (16/14 degrees C) day/night temperatures on growth, photosynthesis, pigment composition and carbohydrate content was compared between domestic and high-altitude wild Lycopersicon species. When related to the relative shoot growth rate (RSGR) measured at optimal temperature, genotypes of the domestic tomato (L. esculentum (L.) Mill. cv. Abunda and cv. Large Red Cherry (LRC) showed a stronger inhibition of RSGR at suboptimal temperature than the high-altitude wild species L. peruvianum Mill. LA 385 and L. hirsutum Humb. & Bonpl. LA 1777. The initiation rare of new leaves was 2.1-fold faster in all species at 25/20 degrees C than at 16/14 degrees C. In contrast to the other genotypes, the leaf area of suboptimally grown Abunda plants was 28 % smaller than the area of leaves that were fully expanded at optimal temperature. In all species, specific leaf area (SLA) at 16/14 degrees C was 17-26 % lower than at 25/20 degrees C. The percentage of leaf dry matter increased in response to growth ar suboptimal temperature. This increase was higher in L. esculentum genotype Abunda (99 %) than in genotype LRC (38 %), and the wild species L. peruvianum (50 %) and L. hirsutum (38 %), which could be attributed to inter- and intra-specific differences in starch accumulation of 16/14 degrees C-grown leaves. Only in both L. esculentum genotypes, net photosynthetic rate at growth irradiance (A(225)) and at light saturation (A(sat)) was 14 to 30 % lower in leaves grown and measured at suboptimal temperature, compared with leaves grown and measured at optimal temperature (25 degrees C). Chlorophyll (Chl) a fluorescence measurements indicated that the decrease of A225 in leaves of suboptimally grown L. esculentum plants was paralleled by a decrease in the quantum yield of photosystem II electron transport (Phi(PSII)), which could be mainly attributed to a decrease in the photochemical quenching component (q(P)). In all species, the nonphotochemical quenching component (NPQ) was 2 to 4-fold higher at 16/14 degrees C. Growth temperature hardly affected Chi content on a leaf area basis, whereas the content of xanthophyll cycle pigments (violaxanthin + antheraxanthin + zeaxanthin) on a Chi basis was ca. 1.5-fold higher in 16/14 degrees C-grown leaves. The epoxidation state of the xanthophyll cycle pool was only slightly lower in suboptimal leaves due to the moderate growth irradiance.