We studied the drought response of eight commercial hybrid maize lines with contrasting drought sensitivity together with the reference inbred line B73 using a non-invasive platform for root and shoot phenotyping and a kinematics approach to quantify cell level responses in the leaf. Drought treatments strongly reduced leaf growth parameters including projected leaf area, elongation rate, final length and width of the fourth and fifth leaf. Physiological measurements including water use efficiency, chlorophyll fluorescence and photosynthesis were also significantly affected. By performing a kinematic analysis, we show that leaf growth reduction in response to drought is mainly due to a decrease in cell division rate, whereas a marked reduction in cell expansion rate is compensated by increased duration of cell expansion. Detailed analysis of root growth in rhizotrons under drought conditions revealed a strong reduction in total root length as well as rooting depth and width. This was reflected by corresponding decreases in fresh and dry weight of the root system. We show that phenotypic differences between lines differing in geographic origin (African vs. European) and in drought tolerance under field conditions can already be identified at the seedling stage by measurements of total root length and shoot dry weight of the plants. Moreover, we propose a list of candidate traits that could potentially serve as traits for future screening strategies.

No abstract

The suppression of T-cell function by cyclosporin therapy can result in an increase of HPV infection, adding to the proliferative activity of cyclosporin in the oral mucosa.

No abstract

The lack of association between apoplastic O(2)(*-) levels and root growth inhibition under hyper-osmotic stress leads us to hypothesize that under those conditions the role of apoplastic O(2)(*-) may be to participate in signalling processes, that convey information on the nature of the substrate that the growing root is exploring.

Sunflower (Helianthus annuus L.) has been rated as moderately salt-resistant, and variability for salt resistance has been detected within this crop. However, variability in salt-resistance mechanisms has not been assessed. Osmotic tolerance, the relation of salt resistance with whole-plant Na + and K + distribution and tissue Na + tolerance were investigated in several sunflower inbred lines. Plants were grown under controlled conditions, in pots with sand and perlite irrigated with salinized (NaCl, -0.65 MPa) nutrient solution. Osmotic tolerance was assessed from the initial effects of the salt treatment on plant elongation in eleven sunflower lines. Longterm salinity responses were evaluated in four of those lines, by assessing whole-plant growth. A principal components analysis (PCA) was run on relative-to-control growth data, and this information was used to establish a relative resistance ranking, which indicated lines HAR2 > HAR1 > HA64 > HAR5. Osmotic tolerance was observed in HA64 and HAR2. The lines showed different degrees of Na + accumulation, it was very low in some of them, but relative salt resistance was not associated to this trait. Tissue Na + tolerance was deduced by comparing the percentage of dead leaves as a function of leaf blade Na + accumulation, and it was higher in HAR1 than in the rest. These results indicate that variability for salt-resistance mechanisms exists in sunflower. Osmotic tolerance and tissue Na + tolerance were detected in different lines, highlighting that such variability may be exploited for increasing salt resistance in this crop.

This work assessed intracultivar variability for salt tolerance within Panicum coloratum cv. Klein, explored some physiological parameters potentially associated with it and evaluated the contribution of cell division and expansion to the decreased leaf length observed under salinity. Individual plants that had survived severe stress environments in an established pasture were collected and clonal families were obtained by vegetative propagation. These were evaluated in a greenhouse, in pots with an inert substrate irrigated with nutrient solution containing 0, 200 or 400 mm NaCl. Salt tolerance was assessed from growth variables expressed as a percentage of non‐salinized controls. Changes induced by salinity in carbon fixation, soluble sugars and compatible solutes were also measured. The selected plants showed 33% higher salt tolerance than plants from the same cultivar obtained from seeds, and variability for salt tolerance was detected within the group, suggesting these plants could be valuable germplasm for breeding programmes for saline areas. All selected plants accumulated low leaf blade Na concentrations (< 0·1 mm g−1 dry weight on average), and K concentrations tended to remain high under salinity. A kinematic analysis indicated a reduction in the number of cells in the division‐only zone was the main cause of shorter leaves under stress. Although plants showed some differences in all these traits, they were not related to salt‐tolerance variability within this group of stress‐tolerant plants.

No abstract