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Salinity is one of the most important abiotic stresses that negatively affects plant growth and development around the world. It has been reported that approximately 19.5% of all irrigated land and 2.1% of dry land is affected by salt stress, and these percentages continue to increase. Sorghum, a C4 plant, is the fifth most important cereal in the world. Numerous studies reported that there are high genetic variations in sorghum. These genetic variations can be monitored to search for the most salt-tolerant genotypes. Therefore, the aim of our study was to investigate the responses of ten sorghum genotypes to different levels of salinity. We focused on germination and seedling growth as the most critical stages of plant development. In our research we included germination percentage, germination index, mean germination time, seedling vigor index, seedlings’ shoot and root lengths, fresh and dry seedling weight, and salinity tolerance indices. For data assessment we applied two-way ANOVA, non-metric multidimensional scaling, and hierarchical agglomerative classification. Our results demonstrate that salinity was responsible for 98% of the variation in assessed parameters, whereas genotype effect accounted for only 2% of the documented variation. It can be concluded that seedling traits can be used as a valid criterion for the selection of genotypes with a better tolerance to salinity stress.

SU MMARYCompared with growth at 20/15 xC (day/night), exposure of wheat (Triticum aestivum L.) plants to moderately high temperature (30/25 xC) significantly decreased grain weight through shortening the duration of grain filling, combined with small (or no) positive increases in the rate of grain filling. Several mathematical models of grain filling were assessed for their suitability as means of analysing these effects of temperature. The ordinary logistic model was found to be the most appropriate model and was used for the analysis of grain filling responses in four cultivars differing in their responses. Genotypic variation in response to temperature was observed for both rate and duration of grain filling, but the variation for the duration of grain filling among cultivars was small at the higher temperature. Significant correlation was found between single grain weight with the rate, but not with the duration, of grain filling at high temperature, which indicated an important role for synthetic processes involved in grain filling in the temperature sensitivity of wheat cultivars. As they are independent traits, both rate and duration are required selection criteria for the improvement of heat tolerance. Responses of one attribute estimated from the logistic model, the inflection point of the course of grain filling, may give insight into a temperature response that is distinguishable from that associated with the duration of grain filling. The inflection point appears to be worth including as a criterion in selecting for high temperature tolerance in wheat.

In this study, we investigated the responses of cells acclimated to 300 µmol m s photon flux density to an increase (1000 µmol m s) or decrease (30 µmol m s) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a rearrangement of carbon metabolism towards the production of phosphoenolpyruvic acid (PEP) and/or pyruvate. These intermediates were used differently by the cell as a function of the photon flux density: under low light, photosynthesis was depressed while respiration was increased. Under high light, lipids and proteins accumulated. Of great interest, under high light, the genes coding for the synthesis of aromatic amino acids and phenolic compounds were upregulated suggesting that the shikimate pathway was activated.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'.