Huguette Sallanon

Relationship between PSII activity, CO2 fixation, and Zn, Mn and Mg contents of Lolium perenne under zinc stress

Summary The effect of zinc toxicity on photosystem II (PSII) activities, photosynthetic function, and some mineral concentrations in hydroponically-grown Lolium perenne was studied at four ZnSO 4 concentrations (1, 5, 10, and 20 mmol/L) in the nutrient solution. Ryegrass showed a very strong capacity to protect itself against toxic zinc concentrations, requiring a large amount of ZnSO 4 (20 mmol/L) to inhibit growth. In the leaves, the increase in zinc content was accompanied by an increase in manganese concentration, which never reached a toxic level. This increase in manganese concentration may limit the decrease in the F v /F m ratio and ΦPSII due to zinc stress, and thus granting zinc resistance to ryegrass. The net photosynthesis rate was significantly reduced, and after 15 days, with a zinc concentration of 2.7 mg g −1 DW in the leaves, the carboxylase activity was nearly nil. At the same time, the oxygenase activity of RuBisCO was unaffected or even increased, another possible contribution to the tolerance of ryegrass to excess zinc. The carboxylase and oxygenase activities of RuBisCO were identical (93 μmol (e − ) m −2 s −1 ) with a zinc concentration in the leaves of 1.6 mg g −1 DW after 8 days and 1.4 mg g −1 DW after 15 days, corresponding to 5 mmol/L zinc and 1 mmol/L zinc in the growth medium, respectively.

Treatment of domestic wastewater by an hydroponic NFT system

The objectives in this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. A commercial hydroponic system was adapted for this study and the wastewater was used to irrigate Datura innoxia plants. Influent and effluent samples were collected once a month for six months and analysed to determine the various parameters relating to the water quality. The legal discharge levels for total suspended, biochemical oxygen demand and chemical oxygen demand were reached with the plant system after 24 h of wastewater treatment. Total nitrogen and total phosphorus reduction were also obtained. NH4(+)-N was reduced by 93% with nitrification proving to be the predominant removal process. Significant nitrification occurred when the BOD5 level dropped 45 mg/l. Similar results were obtained for six months although the sewage composition varied widely. D. innoxia develops and uses the wastewater as the unique nutritive source.

Influence of growth room and vessel humidity on the in vitro development of rose plants

An increase of the vapor pressure deficit (VPD) of the growth room atmosphere (from 600 Pa up to 2000 Pa) induced a variation in the air VPD inside the vessels used for rose micropropagation.During the photoperiod, the in vitro plants lost water by evaporation. During the night period, depending upon the VPD of the growth room, plants could take water from the vessel atmosphere.According to the intensity of the transpiration, large changes in the growth and morphology were observed: decrease in multiplication rate, modification of leaf colour and area, reduction of the elongation and changes of the level of axillary buds which grew.

Cryopreservation of Chrysanthemum cinerariaefolium Shoot Tips

Summary A simple method for efficient cryopreservation of Chrysanthemum cinerariaefolium shoot tips is described. It comprises the following steps: treatment of the explanted shoot tips with 0.55 mol/L sucrose plus 4 µmol/L ABA for 3 days, direct immersion in liquid nitrogen, rapid rewarming at 40 °C and recovery of the shoot tips on solid nutrient medium containing 11 µmol/L ANA and 4.5 µmol/L BAP About 75 % of the shoot tips withstood cryopreservation using this procedure. The morphogenic potential of frozen shoot tips, and total chlorophyll and pyrethrin contents of regenerated plants were preserved after the different treatments.

Growth and gas exchange responses of Hevea brasiliensis seedlings to inoculation with Glomus mosseae

Abstract The beneficial effect of arbuscular mycorrhizal (AM) fungi on plant growth is well known, but the physiological processes involved are still discussed. The purpose of this study was to determine if Glomus mosseae affects the growth of Hevea brasiliensis seedlings and, if it is the case, if it could be associated with variations in leaf CO2 and H2O gas exchange. H. brasiliensis rubber trees were grown for 9 months in a medium containing either propagules of G. mosseae or sterilized inoculum. Plant size, root collar diameter and leaf area, as well as net CO2 assimilation, stomatal conductance (gs) and water-use efficiency of photosynthesis were evaluated during the first 5 stages of growth. At stage 2, a growth depression occurred in the mycorrhizal seedlings coincident with the first AM infections. Then, at stage 5, Glomus mosseae-inoculated plants had moderate colonization (47% of root length) and were taller than control plants with a larger root collar diameter and an enhanced leaf organogenesis. This enhanced growth was accompanied by increased photosynthesis, transpiration, and stomatal conductance. After 9 months, dry weights of shoots and roots of inoculated plants were greater than those of controls by 27 and 17%, respectively.

Response of the physiological parameters of mango fruit (transpiration, water relations and antioxidant system) to its light and temperature environment

Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared. Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate. Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality.

The ultrastructure of micropropagated and greenhouse rose plant stomata

Stomata of leaves from in vitro grown rose plantlets remain opened in the dark. The ultrastructure of their guard cells was studied after a 7 h light and a 7 h dark period, and compared to that of functional stomata from plants which have been acclimatized to greenhouse conditions. Qualitative and quantitative observations concerning the shape of the guard cells, mitochondria, plastids and starch grains, demonstrated the similarity in guard cell ultrastructure. The peculiarity of guard cell ultrastructure of in vitro cultured plants was the inability to close in the dark; vacuolar area was 40% of the whole guard cell area during both light and dark period whereas, in guard cells from greenhouse plants, the vacuolar area was 40% of the whole guard cell area during the light and only 25% during the dark period. These results indicate that stomata from in vitro plants are duly developed and possess an ultrastructure suitable for a typical functioning. The inability to close in the dark results from atypical water relation.

Photosynthetic activity of Lolium perenne as a function of endophyte status and zinc nutrition

Grass infection by endophyte fungi can confer host resistance to different types of stress, but limited evidence is available on the related effects on the photosynthetic mechanism of the grasses. Zinc has direct and indirect effects on this mechanism and is one of the more important environmental pollutants. To measure whether photosynthesis of the host plant is affected by fungal infection when endophyte-free and endophyte-infected grasses contain similar excess zinc concentrations in their leaves, two batches of Lolium perenne L. cv. Apollo plants were established, one batch was infected with Neotyphodium lolii, the other was not. Both batches were then treated for 8 d with a nutrient solution containing 0, 1, 5, 10 or 20 mm ZnSO4. The increase in zinc concentration induced some reduction in photosystem II (PSII) activity but not enough to account for the total drop in the net photosynthetic rate. Endophyte fungus favoured maintenance of the PSII activity, but did not significantly modify the net photosynthesis and similar zinc concentration levels were observed in leaves of both types of plant. Interactive effects of zinc and light induced less photodamage to the PSII of the host, which is able to react to an increase in photon flux density (PFD). In endophyte-free plants, the reaction centre contributed more than antenna complexes to energy dissipation. In endophyte-infected plants, the quenching of the reaction centre and antenna complexes rose simultaneously and at a constant rate, as zinc concentrations increased.

Cryopreservation of Chrysanthemum cinerariaefolium Vis. cells and its impact on their pyrethrin biosynthesis ability

Abstract An efficient protocol for cryogenic storage of high-pyrethrin-producing cell lines of Chrysanthemum cinerariaefolium is described. Optimal survival (92%) was obtained with cells precultured in 1/2 Murashige and Skoog nutrient medium containing 180 g ⋅ l–1 sucrose for 30 days, then incubated in the same medium in the presence of 5% DMSO for 1 h in an ice bath, cooled slowly to –20°C and immersed for 30 min in liquid nitrogen. After cryopreservation, the cells conserved the same growth pattern, but displayed different biochemical properties. The subculture derived from the thawed cells was characterized by a lower chlorophyll content and a higher pyrethrin biosynthesis ability.

Rapid mass propagation of Chrysanthemum cinerariaefolium Vis. by callus culture and ability to synthesise pyrethrins

Abstract Rapid mass propagation of Chrysanthemum cinerariaefolium from young flower heads was developed to compare the ability of callus, in vitro shoots and rooted plants, and original plants to synthesize pyrethrins. The ability to synthesise all six pyrethrin components increased with differentiation. Jasmolin II and cinerin II were the main products present in mother plant shoots, whereas pyrethrin I was the greater component present in callus and in vitro plants. Clonal propagation increased the pyrethrin I content compared to that of plant shoots and young flowers. Total pyrethrin content was the same in in vitro and plant shoots, but lower in these shoots than in young flowers. The pyrethrin I/pyrethrin II ratio, which is directly related to insecticidal activity, varied from 3.4 in in vitro shoots to 0.87 in mother plant shoots and young flowers.