Fatiha Aid

Effect of drought stress on the photosynthesis of Acacia tortilis subsp. raddiana at the young seedling stage

Water stress usually impairs photosynthesis and plant growth. Acacia tortilis subsp. raddiana is well adapted to dry environments. The aim of the present study was to determine the impact of a progressive decrease in soil water content on photosynthetic-related parameters at the young seedling stage. Drought-induced plant responses occurred according to two types of kinetics. Water potential, stomatal conductance, and transpiration rates were rapidly affected by a decrease in soil water content, while chlorophyll fluorescence-related parameters and chlorophyll concentrations decreased only when soil water content was lower than 40%. The maximal efficiency of PSII photochemistry in the dark-adapted state remained unaffected by the treatment, whatever the stress duration. A. raddiana accumulated high concentrations of soluble sugars in relation to a stress-induced early stimulation of sucrose-phosphate synthase activity, while stimulation of invertase and sucrose synthase led to fructose accumulation only at the end of the stress period. We suggested that sugar accumulation may be involved in osmotic adjustment and protection of stressed tissues. A. raddiana was thus able to protect its photosynthetic machinery under drought conditions and may be considered as a promising species for revegetation of dry areas.

Intraspecific variability of carbon isotope discrimination and its correlation with grain yield in safflower: prospects for selection in a Mediterranean climate

ABSTRACT The goals of the present study were to obtain a first estimate of intraspecific variability of carbon isotope discrimination (Δ) in safflower, a thistle-like herbaceous plant, and to determine the statistical relationship between Δ and grain yield as well as its components in a collection of 45 accessions of different origins. Grain yield and aboveground biomass, harvest index, average grain weight, and Δ (measured on the bulk leaf organic matter) were investigated in experimental field conditions. A large variability was noted for all traits but a principal component analysis (PCA) allowed to identify several homogeneous groups of accessions. Average grain yield per plant varied between 1 and 39 g. Δ varied between 21.3 and 25.2 ‰, i.e. a large variation of 3.9 ‰. In our experiment, the variation of Δ was not significantly related to that of grain yield in the whole accession sample. However, we found contrasting trends for this relation within accession groups. These initial results motivate further experiments to assess more in depth correlation between Δ and yield in safflower and are encouraging regarding the possibility of using Δ as an effective selection index in safflower to obtain genotypes that efficiently consume water. This study also highlighted one accession that combines the two characters required in the Mediterranean regions, i.e. high yield performance and high water-use efficiency.

Modification of the biosynthesis of rape lipid molecular species by heat shock

Abstract Rape, Brassica napus is a C 16:3 plant, the leaves of which contain mainly “prokaryotic” molecular species † of monogalactosyldiacylglycerol (MGDG) (18 : 3/16 : 3, 76 mol%) and “eukaryotic” molecular species of digalactosyldiacylglycerol (DGDG) (18 : 3/18 : 3, 70 mol%). Phosphatidylglycerol (PG) contains nearly exclusively “prokaryotic” molecular species (18 : 3/16 : 1 t , 18 : 3/16 : 0 and 18 : 2/16 : 1 t ), whereas phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are exclusively formed by “eukaryotic” ( C 18 C 18 , C 16 C 18 ) molecular species. A heat shock provoked a great decrease in [1- 14 C] acetate incorporation into rape leaf lipids, a decrease in the labelling of polyunsaturated fatty acids and an increase in the labelling of palmitic acid. After a heat shock, more saturated labelled molecular species (16 : 0/18 : 2, 16 : 0/18 : 3) appeared in PC and DGDG. The biosynthesis of prokaryotic MGDG molecular species was more inhibited by a heat shock than the biosynthesis of those of eukaryotic MGDG. Heat shock provoked an increase of 18 : 3/16 : 0 and 18 : 2/16 : 0 MGDG molecular species; thus, the chloroplastic palmitoyl MGDG desaturase could be affected.

Interactive effects of salinity and two phosphorus fertilizers on growth and grain yield of Cicer arietinum L.

ABSTRACT Chickpea is considered among the most sensitive grain legumes to salinity. The improvement of tolerance of lines in combination with tolerant rhizobial strains depends on various environmental and cultural conditions such as soil properties. This investigation was undertaken to evaluate the effect of phosphorus fertilization (0, 90 and 200 kg ha−1 of P2O5) on biomass, nodular traits and grain yield (GY) of chickpea (cv. Flip 84-79C) growing under salinity (0 and 150 mM NaCl). The trial was laid out following a randomized block design with three replicates during 2010–2012, at the experimental farm of Oued Smar (Algiers). Salinity did not significantly decrease the dry biomass of the plants but the relative shoot growth was more affected than control, P and SP1 treatments. Besides, salinity significantly reduced GY (−20%) and nodulation traits compared to the control plants while an inversely proportional relationship was found between protein, leghemoglobin and MDA content, K/Na ratio and the increase in salt concentration. Application of two P levels to saline soil enhanced growing conditions of plants. Particularly, the (90 kg ha–1 of P × 150 mM NaCl) combination significantly increased leghemoglobin (92%), reduced proline content (−69%) and protected membranes against peroxydation compared to saline conditions. A significant increase was observed in the GY (about 30%) of plants at both P doses combined with salt stress compared to other cases. Statistically, the low P level combined with salinity induced similar responses of plants and sometimes better responses to control plants. Finally, our results support the roles of phosphorus fertilizer in the alleviation of salt stress and enhancing the soil quality for better symbiosis efficiency and yield of chickpea.

Effects of a Heat Shock on the Molecular Species of Rape Polar Lipids

Rape (Brassica napus L. var Bienvenue) is an oil seed plant of great potential economical interest for Algeria. The main problem for growing rape in this country is the high environmental temperature encountered during summer. Growth at high temperature results in a decrease in the abundance of polyunsaturated fatty acids. Such a decrease is associated with reduced membrane fluidity [1].

Relationship between taproot morphological traits, carbon isotope composition and grain yield in safflower

Abstract The purpose of this study was to determine to what extent root characteristics, other than the taproot length, contribute to high grain yield and/or high water use efficiency (WUE) in safflower. A greenhouse trial was conducted using four safflower accessions (USDA6, USDA23, USDA29 and VARTOUG) with contrasting yield and WUE. A randomised complete block design was chosen, which included a typical (control) and a drought stress (withholding watering at the pre-flowering stage) treatments. The carbon isotope composition (δ13C) as an estimate of WUE, taproot diameter (DTR), diameter and number of secondary roots (DSR and NSR, respectively), biomass of the upper section of the taproot (BMTR-up) as well as grain yield (GY) and its components were measured. Our results revealed that NSR could be involved in drought adaptation of USDA23, with NSR increasing significantly (p = 0.045) by 27% under drought stress in this accession. BMTR-up was the only taproot trait correlated to GY and/or WUE, however the nature of the correlation was different for control and stressed plants. BMTR-up was significantly (p = 0.01) and negatively correlated with δ13C (r = –0.63) but had no correlation with GY (r = 0.23) in control plants. In contrast, BMTR-up was significantly (p = 0.03) and positively correlated with GY (r = 0.56) but not with δ13C (r = 0.23) under drought stress conditions. This finding suggests that, in the absence of drought conditions selecting safflower for a lower biomass in the upper section of the taproot may lead to high WUE, without affecting the yield.

Enhancing of symbiotic efficiency and salinity tolerance of chickpea by phosphorus supply

ABSTRACT This study aims to highlight the beneficial effect of the phosphorus on enhancing of growth plant, the efficiency of use rhizobial symbiosis and ionic partition in chickpea grown under salt stress. Exposure of plants to salt stress (0, 150 mM of NaCl) caused ionic imbalance, which resulted in increased Na+ and P and reduced K+ contents in the leaves and root. Indeed, stressed plants showed decrease of plant growth and phosphorus use efficiency. The efficiency use of rhizobial symbiosis was also affected by salinity. However, addition of two different level of phosphorus (37 and 55 mM) to saline soil increased significantly availability of P in plant organs. Specially, the (150 mM NaCl × 37 mM P) mixture increased (33%) phosphorus use efficiency, induced better nodulation and increased plant biomass which results in the high efficiency in use of the rhizobial symbiosis. Our findings suggest that the combination of low level of P to saline soil presumably improved the tolerance of chickpea plant to salinity. Abbreviations: phosphorus (P); phosphorus use efficiency (PUE); biological nitrogen fixation (BNF); plant dry weight (PDW); yeast extract mannitol (YEM); efficiency in use of the rhizobial symbiosis (EURS); shoot dry weight (SDW); symbiotic nitrogen fixation (SNF).

Phylogenetic position of two endemic Carthamus species in Algeria and their potential as sources of genes for water use efficiency improvement of safflower

Despite the high economic value of safflower (Carthamus tinctorius), the potential of several wild related species as genetic resources is still poorly studied, in particular with regards to drought tolerance, a priority in safflower improvement. This situation is partially explained by the numerous and still discussed uncertainties in phylogenetic relationships within the safflower species complex. In this study, we focused on two rare Algerian wild species, Carthamus strictus and Carthamus chouletteanus. We aimed at: (i) clarifying their taxonomic status, and determining their phylogenetic relationships with safflower and other Mediterranean species of Carthamus sensu lato (s.l.) (Carthamus sensu stricto (s.s.) and Carduncellus genera) by using nucleotide diversity within the internal transcribed spacer region (ITS) and (ii) assessing the water use efficiency (WUE) of these species by determining their carbon isotope composition. Our results support the existence of two well supported different clusters among the safflower species complex: Carthamus s.s. including Eastern annual species and the vast Carduncellus group constituted by Western perennial species, including the two studied Algerian species. Also, significant differences for carbon isotopic composition between Carthamus s.s. and Carduncellus were revealed. Carduncellus species displayed significantly higher δ13C values (i.e., higher WUE) than Carthamus s.s. species. Carthamus chouletteanus displayed the highest average value of δ13C (highest WUE) among the species studied. Our data encourage for further studies on the possibility of hybridisations between species of the two genera and suggest that Carduncellus should be considered as potentially more interesting genetic resources to improve the WUE of safflower, rather than Carthamus s.s. species.