Chill-induced reactions in poplar

The aim of this work is to study the behaviour of a poplar clone under chilling stress conditions. Two experimental systems constituted of plants or detached leaves of cuttings of Populus tremula x Populus tremuloides cv. Muhs 1 were submitted to chilling (4 °C) and control (23 °C) conditions. During 4 days, sampling was realised. The first step of the work consisted in the observation of the effects of chilling on stress indicators, i.e. chlorophyll fluorescence as well as chlorophyll content. Chlorophyll fluorescence indicated that the plants were stressed. Similarly, increasing sucrose and glucose levels as well as enhanced sucrose metabolism in the plants subjected to chilling stress were recorded. The comparison of the proteome of leaves under both conditions revealed the presence of two families of proteins in stressed plants

Genetic structure of common ash in Europe analyzed with nuclear microsatellites

International audienc

Auxin polyamine interaction in the control of the rooting inductive phase of poplar shoots in vitro

Changes in endogenous free IAA and its conjugate IAAaspartate as well as in endogenous polyamines were analysed in in vitro poplar shoots during their inductive phase, under the effect of the rooting auxin NAA, in combination or not with polyamines or inhibitors of polyamine biosynthesis. In vitro raised poplar shoots rooted 100% when treated by NAA (0.3 mg/l) for 7 h, the previously determined duration of the inductive phase. Spermidine and aminoguanidine (AG, an inhibitor of diamine oxidase) alone were unable to promote rooting under these conditions, and counteracted the NAA rooting effect. Putrescine and cyclohexylamine (CHA, an inhibitor of spermidine synthase) on the contrary did not oppose the NAA effect and promoted up to 40% rooting when applied alone. The levels of free indoleacetic acid (IAA) and of its aspartate conjugate IAAsp elevated up to peaks situated at the 7th and 8th h, respectively in the basal parts of the NAA-treated shoots. Putrescine, when added toegether with NAA, did not affect the typical IAA and IAAsp increases (except a displacement of the peaks to the 8th and 10th h, respectively); when applied alone, it provoked elevation of their levels to limited extents. Quite similar results were recorded with CHA. Spermidine and AG counteracted the NAA induced elevations of IAA and IAAsp. The level of endogenous putrescine typically increased up to a peak at the 6th h in the basal part of the NAA-treated shoots only, was slightly affected by exogenous putrescine and CHA application but significantly reduced by spermidine and AG supply. The NAA inducing rooting treatment did not affect the variation of the levels of endogenous spermidine and spermine but putrescine treatment (also spermidine to a lesser extent) led to increases of their levels. The relationships between auxin and putrescine temporary accumulation are discussed as well as the involvement of the different polyamines in the rooting inductive process

Putrescine control of peroxidase activity in the inductive phase of rooting in poplar shoots in vitro, and the adversary effect of spermidine

Poplar shoots raised in vitro rooted by 100 °lo in the presence of an auxin while in its absence they did not root. Putrescine, however, and the inhibitor of spermidine synthase, cyclohexylamine (CHA), which favours putrescine accumulation, were able to promote up to 40 % rooting in the absence of auxin. The inhibitory effect of aminoguanidine (AG), which inhibits diamine oxidase, indicated that the catabolic pathway of putrescine was involved in the rooting process. The inductive phase of rooting in poplar shoots was characterized by an increase of peroxidase activity followed by a rapid decrease. Putrescine and CHA favoured this variation. AG and spermidine had adversary effects

Growth characteristics and biochemical changes of poplar shoots in vitro under sodium chloride stress

The effect of NaCl on poplar shoots grown in vitro was studied. After 28 days of cultivation on media containing up to 300 mmol/L NaCl, the shoot and root lengths as well as the rooting percentage were smaller than in the control. These effects were enhanced by increasing salinity. Changes in several biochemical markers (soluble proteins, soluble sugars and peroxidase activity) were observed in poplar shoots cultivated for 7 days on salt-supplemented and control media. Measurements showed that the soluble protein content of the plants decreased dramatically on day 1 but stabilized to a constant value thereafter, except for the 300 mmol/L NaCl condition. Peroxidase activity increased with salt content and time of cultivation, except for the 300 mmol/L NaCl condition, where it remained unchanged. Changes were also observed in the contents of glucose, fructose, sucrose and galactose. Glucose and fructose contents strongly increased after 3 days of cultivation on 300 mmol/L NaCl-containing medium. A maximum sucrose content was observed on day 1 for all conditions, followed by a decrease until day 7. Galactose was unaffected by the salt treatments

In vitro iron bioaccessibility and uptake from orange-fleshed sweet potato (Ipomoea batatas (L.) Lam.) clones grown in Peru.

Research to evaluate the potential of sweet potato to alleviate iron deficiency in affected human populations in developing countries is scarce. To partly fill this gap, we evaluated the bioaccessibility of iron in six sweet potato clones grown in two Peruvian environments, Satipo and San Ramon, following an in vitro gastro-intestinal digestion procedure. The bioaccessible iron content was clone-dependent and 1.7-fold higher in Satipo (5.15 g/g of fresh weight (FW)) as compared to San Ramon (3.04 g/g of FW). Aspects of iron bioavailability were then investigated using the Caco-2 cell model and ferritin synthesis as a marker, on two sweet potato clones after addition of an extrinsic source of iron to the digestion mixture.Results indicated that clone “CIP-194540.5” was presenting higher bioaccessible iron and lower phenolic contents and showed higher iron uptake as compared to clone “CIP-1055011.1” in both environments (91% vs. 24% in Satipo and 67% vs. 13% in San Ramon, respectively). These iron uptake values are higher than the ones previously reported for potato, which further stresses the use of sweet potato storage roots as part of a healthier diet in developing countries