Effect of acclimation to suboptimal temperature on chilling-induced photodamage: comparison between a domestic abd a high-altitude wild Lycopersicon species

Plants of a domestic (Lycopersicon esculentum [L.] Mill. cv. Abunda) and a high-altitude wild Lycopersicon species (L. peruvianum Mill. LA 385) were grown at near-optimal (25/20 degrees C) or suboptimal (16/14 degrees C) temperature. Leaf discs from just fully expanded leaves were exposed to an irradiance of 1000 mu mol m(-2) s(-1) at 5 degrees C for 48 h. The effect of growth temperature on the susceptibility to photoinhibition of photosystem II (PSII) and its recovery, degradation of leaf pigments, chlorophyll (Chl) fluorescence quenching and xanthophyll cycle activity were examined. Leaves of L. esculentum and L. peruvianum plants grown at optimal temperature, were similarly susceptible to photodamage. Suboptimal-grown leaves of both species showed a higher tolerance to photoinhibition than optimal-grown leaves. In both species, recovery of photoinhibited PSII was more complete in leaves grown at suboptimal than at optimal temperature. In contrast to L. esculentum, suboptimal-grown leaves of L. peruvianum exhibited faster kinetics of recovery from photoinhibition than optimal-grown leaves. Light-induced degradation of leaf pigments in leaves grown at 16/14 degrees C was 2.3- and 2.7-times slower in L. esculentum and L. peruvianum, respectively, when compared with leaves grown at 25/20 degrees C. Non-photochemical quenching (NPQ) of Chl fluorescence developed faster in leaves of suboptimal-grown plants. and steady-slate levels were similar to 20% higher than in leaves of optimal-grown plants of both species. An increased pool size of xanthophyll cycle pigments together with a slightly higher conversion state, resulted in a 1.5- (L. esculentum) or 3-fold (L. peruvianum) higher maximal zeaxanthin content in suboptimal-, as compared with optimal-grown leaves. These results demonstrate that acclimation to suboptimal temperature increased the capacity to resist chilling-induced photodamage in both the domestic and the high-altitude wild Lycopersicon species. However. the acclimatory response was more pronounced in L. peruvianum than in L. esculentum, indicating a greater ability of the high-altitude wild species to acclimate its photosynthetic apparatus to suboptimal temperatures. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved

Impact of suboptimal temperature on growth, photosynthesis, leaf pigments and carbohydrates of domestic and high-altitude wild Lycopersicon species

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

Chilling-induced photoinhibition in nine isolates of Valonia utricularis (Chlorophyta) from different climate regions

Chilling induced inhibition of photosynthesis was studied in nine isolates of the marine tropical to warm-temperate green macrophyte Valonia utricularis (Roth) C. Agardh. According to their temperature requirements for growth and survival, the isolates belong to a cold-tolerant Atlantic/Mediterranean group and a cold-sensitive Indo-west Pacific group. After 5 hours exposure to 5 degreesC under moderate light, all isolates experienced similar substantial photoinhibition, which approached steady state levels after a decline in Fv/Fm to about 40 % of the initial values. After return to optimal temperature and dim light conditions, Fv/Fm values increased with biphasic kinetics. A fast phase with half-life times of less than 30 minutes (dynamic photoinhibition) was followed by a slow phase lasting a few hours, indicating repair of photodamaged PSII reaction centres (chronic photoinhibition). In the Atlantic/Mediterranean isolates the fast phase accounted for more than 80 % of the recovery response, showing that these isolates were able to cope with the applied low temperature stress by down-regulating their PSII reaction centres. In contrast, the two isolates from the Seychelles were predominantly photodamaged. In a second experiment, three isolates (Corsica, Seychelles, Japan) were exposed to a similar relative amount of cold stress (0, 10, 15degreesC, respectively). The Japanese isolate and the isolate from the Seychelles showed significantly less inhibition compared to 5 degreesC exposure, but no significant difference was found in the Corsican isolate. However, the degree of low temperature stress had no significant influence on the relative contributions of dynamic and chronic photoinhibition. Only two of the seven investigated isolates had a lower final inhibition level when grown at sub-optimal temperatures than at optimal temperatures. However, all sub-optimally grown Atlantic/Mediterranean isolates exhibited faster recovery kinetics from chilling-induced photoinhibition than optimally grown plants. This is related to a faster recovery from chronic photoinhibition than to a higher relative contribution of dynamic photoinhibition. A specific role of the photoprotective pigments of the xanthophyll cycle, leading to an acclimation response in the Atlantic/Mediterranean isolates may be involved. We conclude that ecotypic differentiation in V utricularis is mirrored in different degrees of susceptibility to low temperature stress