22 research outputs found
Influence of Water Stress on Seed Germination Characteristics in Invasive Diplotaxis harra (Forssk.) Boiss (Brassicaceae) in Arid zone of Tunisia
Diplotaxis harra (Forssk.) Boiss (Brassicaceae) has a wide ecological and geographical amplitudes in Tunisia and grows under a variety of environmental conditions. A laboratory experiment was performed to evaluate the effect of water potential on seed germination and recovery responses after transfer to distilled water. The germination responses of seeds at 15ĂâĂ°C in complete darkness were determined over a wide range of PEG-6000 solutions of different osmotic potentials: 0 to Ă¹ùâÂŹĂąâŹĆ1 MPa. Greatest germination was obtained in distilled water (71%), and increases in osmolality of solutions progressively inhibited seed germination, less than 10% of the seeds germinated at Ă¹ùâÂŹĂąâŹĆ0.8 MPa. No germination was observed for the treatment of Ă¹ùâÂŹĂąâŹĆ1 MPa. The rate of germination decreased as osmotic potential decreased. When seeds were transferred to distilled water after 20 days of water stress, the recovery of germination increased with an increase in pretransfer PEG-6000 treatments. Seeds subjected to high osmotic potential had higher recovery percentages. ĂâĂ
Factors influencing seed germination of medicinal plant Salvia aegyptiaca L. (Lamiaceae)
AbstractSalvia aegyptiaca is a xerophytic perennial herb belongs to the Lamiaceae family commonly used for medicinal purposes. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after transferring to distilled water. Temperatures between 10 and 40°C seem to be favourable for the germination of this species. Germination was inhibited by either an increase or decrease in temperature from the optimum (30°C). The highest germination percentages were obtained at 0mM NaCl; however, the increase of solution osmolalities progressively inhibited seed germination. The germination rate decreased with an increase in salinity for most of tested temperatures, but comparatively higher rates were obtained at 30°C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 300mM NaCl. By experimental transfer to distilled water, S. aegyptiaca seeds that were exposed to moderately saline conditions recovered and keep their ability to germinate mostly at low temperatures. At 300mM NaCl, germination recovery decreased with increasing temperature and it was completely inhibited at 40°C
Facteurs influençant la germination des graines de Cleome ambyocarpa Barr. & Murb. (Capparidaceae) dans le Sud tunisien
Cleome amblyocarpa Barr. & Murb. is an annual herb in the family of Capparidaceae.
It is abundant in sandy environments, and the gravel and stony grounds in Tunisian arid areas. Laboratory
experiments were carried out to assess the effects of temperature (10 to 40° C) on seed germination in
complete darkness. The osmotic stress simulated by NaCl at different concentrations (0 to 200 mM) or
polyethylene glycol 6000 (PEG-6000) at different osmotic potentials (0 to -1 MPa) was evaluated at the
most suitable temperature found. Greatest germination percentage and rate of germination were obtained
at 25° C, but germination was inhibited by either an increase or decrease in temperature from the optimal
temperature. The increase in osmolality of solutions induced by NaCl or PEG progressively inhibited seed
germination. At 150 mM NaCl or osmotic potential of -0.6 MPa, germination was completely inhibited.
There was a decrease in the rate of germination as osmotic stress was intensified. These findings suggest that
C. amblyocarpa was able to tolerate well osmotically- and saline-stressful habitats of the arid ecosystems
during germination stageCleome amblyocarpa Barr. & Murb. est une plante herbacée annuelle de la famille des Capparidaceae. Elle est abondante dans les environnements sableux, les sols secs et pierreux, ainsi que les alluvions de gravier dans les
zones arides tunisiennes. Des expériences conduites au laboratoire ont été effectuées pour évaluer les effets de la température (10 à 40° C) à l'obscurité. Le stress osmotique simulé par le NaCl à différentes concentrations (0 à 200 mM) ou le polyéthylÚne glycol 6000 (PEG-6000) à différents
potentiels osmotiques (0 à -1 MPa) a été évalué à la température optimale trouvée. Les meilleurs pourcentages et vitesses de germination ont été obtenus à 25° C, mais la germination est inhibée au-dessus et en deçà de cette température. L'augmentation de l'osmolarité des solutions induites
par le NaCl ou le PEG inhibe progressivement la germination des graines. à 150 mM NaCl ou un potentiel osmotique de -0,6 MPa, la germination est complÚtement inhibée. On assiste à une diminution de l'indice de germination au fur et à mesure que le stress osmotique est accentué. Ces résultats
suggÚrent que C. amblyocarpa semble bien tolérer la salinité et la sécheresse des écosystÚmes arides durant la phase germinative
Morpho-phenological variability in nine wild Rosy Garlic (Allium roseum L.) accessions from Tunisia
This study aims to compare the morpho-phenological variability of nine accessions
of Allium roseum L. from different bioclimatic zones of central and southern Tunisia. Results showed the
presence of a large morpho-phenological diversity among the studied accessions. The number of homogeneous
groups formed after multiple comparisons of means, ranging from two (for the descriptor average
number of leaves) to seven (for descriptors average length of the flower stalk and average length of the
vegetative phase). A principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used
to determine the nature and degree of divergence among accessions and the total variation was explained to
nearly 86.6 % for the three main components. The HCA showed that these accessions are grouped into three
classes that show a certain affinity among accessions according to their geographical origin. The accessions
with the highest leaf number (vigorous) and which have the longest vegetative phase are Sidi Bou Ali and
Bir Ali. The latest provenances are: Sidi Bou Ali, Bir Ali, Lemaya and El Jem. These accessions are from the
Sahel and central Tunisia. For both inflorescence number and vegetative vigour, it appears that accessions
that have the highest reproductive and vegetative vigour are Sidi Bou Ali, Bir Ali and Lemaya originated
from the Sahel and central Tunisia. The difference South-North is once again evident as regards the average
number of seeds. Indeed, we note that the accessions from the South produced more seeds than the North.
These results are of great interest for future breeding program for this species known for its culinary and
therapeutic propertiesCette étude a pour objectif de comparer la variabilité morpho-phénologique de neuf accessions d'Allium roseum L. en provenance de différentes zones bioclimatiques de la Tunisie centrale et méridionale. Les résultats obtenus ont
permis de mettre en évidence la présence d'une grande diversité morpho-phénologique entre les accessions étudiées. Le nombre de groupes homogÚnes, formés aprÚs comparaison multiple des moyennes, varie de deux (pour le descripteur nombre moyen des feuilles) à sept (pour les descripteurs
longueur moyenne de la hampe florale et durée moyenne de la phase végétative). Une analyse en composantes principales (ACP) et une classification ascendante hiérarchique (CAH) ont permis de déterminer la nature et le degré de divergence entre les accessions et la variation totale a été
expliquée à prÚs de 86,6 % par les trois composantes principales. La CAH a montré que ces accessions se regroupent en trois classes qui mettent en évidence une affinité entre certaines accessions en fonction de leur origine géographique. Les accessions les plus feuillues (vigoureuses) et qui
prĂ©sentent la phase vĂ©gĂ©tative la plus longue sont Sidi Bou Ali et Bir Ali. Les provenances les plus tardives sont: Sidi Bou Ali, Bir Ali, Lemaya et El Jem. Il s'agit d'accessions en provenance du Sahel et du centre du pays. Aussi, pour le nombre d'inflorescences et la vigueur vĂ©gĂ©tative Ă
la fois, il s'avÚre que les accessions qui présentent les plus fortes vigueurs végétative et reproductive sont celles de Sidi Bou Ali, Bir Ali et Lemaya. Il s'agit toujours d'accessions en provenance du Sahel et du centre du pays. La différence Sud-Nord est encore une fois évidente en ce qui
concerne le nombre moyen de graines. En effet, on remarque que les accessions en provenance du Sud produisent plus de graines que celles du Nord. Ces rĂ©sultats sont d'un grand intĂ©rĂȘt pour un futur programme d'amĂ©lioration gĂ©nĂ©tique chez cette espĂšce connue par ses propriĂ©tĂ©s thĂ©rapeutiques
et culinaires
Rapid recovery of photosynthesis and water relations following soil drying and re-watering is related to the adaptation of desert shrub Ephedra alata subsp. alenda (Ephedraceae) to arid environments
Ephedra alata subsp. alenda is the most important pioneer plant of the moving and semi-stable sand dunes in the deserts and steppes of south Tunisia and occurs naturally in the Grand Erg Oriental, one of the most extreme habitats for plant growth on the planet. A new analysis of physiological performance of this medically important and internationally threatened xerophytic shrub was conducted to assess possible mechanisms of drought tolerance and how these relate to its ecological success. Five-month old plants, grown under controlled climatic conditions, were subjected to a well-watered control treatment or progressive drought by withholding water for 14d with subsequent recovery for 7d. Soil water depletion significantly reduced stem relative water content (RWC) water potential (Κw) and osmotic potential (ΚÏ). Ephedra displayed more negative Κw and ÎšÏ values of ca. -3.5 and -4.1MPa, respectively, at the end of the drought treatment, and were associated with turgor loss. Low stem Κw reduced stomatal conductance (gs), photosynthetic CO2 assimilation rates (ACO2), transpiration (E) and internal CO2 concentration (Ci). However, instantaneous (WUE; ACO2 E-1) and intrinsic (WUEi; ACO2 gs-1) water use efficiency (WUE) increased gradually as water deficit was intensified. Stomatal closure therefore only exerted limited control against dehydration and could not compensate for decreases in soil water status, typical of anisohydric behavior. Drought-stressed stems accumulated high levels of proline up to 480% of control values, highlighting a pivotal role in osmotic adjustment during intense water deficit. In contrast, the osmotic adaptation to soluble sugars was limited. Drought-stressed plants increased ACO2, E, gs and Ci and decreased WUE and WUEi during the first 48h after re-watering, such that they reached similar values to those of control plants by the end of the experiment. Stem proline levels of drought-stressed plants returned to near control values with re-watering. Overall, rapid recovery of photosynthesis following drought-breaking moisture appears to be a critical mechanism allowing E. alata to withstand and survive dry environments
Rapid recovery of photosynthesis and water relations following soil drying and re-watering is related to the adaptation of desert shrub Ephedra alata subsp. alenda (Ephedraceae) to arid environments
Factors influencing seed germination of Cleome amblyocarpa Barr. et Murb. (Capparidaceae) occurring in southern Tunisia
Cleome amblyocarpa Barr. & Murb. is an annual herb in the family of Capparidaceae. It is abundant in sandy environments, and the gravel and stony grounds in Tunisian arid areas. Laboratory experiments were carried out to assess the effects of temperature (10 to 40° C) on seed germination in complete darkness. The osmotic stress simulated by NaCl at different concentrations (0 to 200 mM) or polyethylene glycol 6000 (PEG-6000) at different osmotic potentials (0 to -1 MPa) was evaluated at the most suitable temperature found. Greatest germination percentage and rate of germination were obtained at 25° C, but germination was inhibited by either an increase or decrease in temperature from the optimal temperature. The increase in osmolality of solutions induced by NaCl or PEG progressively inhibited seed germination. At 150 mM NaCl or osmotic potential of -0.6 MPa, germination was completely inhibited. There was a decrease in the rate of germination as osmotic stress was intensified. These findings suggest that C. amblyocarpa was able to tolerate well osmotically-and saline-stressful habitats of the arid ecosystems during germination stage.Facteurs influençant la germination des graines de Cleome ambyocarpa Barr. & Murb.
(Capparidaceae) dans le Sud tunisien.
Cleome amblyocarpa Barr. & Murb. est une plante herbacĂ©e annuelle de la famille des Capparidaceae. Elle est abondante dans les environnements sableux, les sols secs et pierreux, ainsi que les alluvions de gravier dans les zones arides tunisiennes. Des expĂ©riences conduites au laboratoire ont Ă©tĂ© effectuĂ©es pour Ă©valuer les effets de la tempĂ©rature (10 Ă 40° C) Ă lâobscuritĂ©. Le stress osmotique simulĂ© par le NaCl Ă diffĂ©rentes concentrations (0 Ă 200 mM) ou le polyĂ©thylĂšne glycol 6000 (PEG-6000) Ă diffĂ©rents potentiels osmotiques (0 Ă -1 MPa) a Ă©tĂ© Ă©valuĂ© Ă la tempĂ©rature optimale trouvĂ©e. Les meilleurs pourcentages et vitesses de germination ont Ă©tĂ© obtenus Ă 25° C, mais la germination est inhibĂ©e au-dessus et en deçà de cette tempĂ©rature. Lâaugmentation de lâosmolaritĂ© des solutions induites par le NaCl ou le PEG inhibe progressivement la germination des graines. Ă 150 mM NaCl ou un potentiel osmotique de -0,6 MPa, la germination est complĂštement inhibĂ©e. On assiste Ă une diminution de lâindice de germination au fur et Ă mesure que le stress osmotique est accentuĂ©. Ces rĂ©sultats suggĂšrent que C. amblyocarpa semble bien tolĂ©rer la salinitĂ© et la sĂ©cheresse des Ă©cosystĂšmes arides durant la phase germinative.Tlig Tahar, Gorai Mustapha, Neffati Mohamed. Factors influencing seed germination of Cleome amblyocarpa Barr. et Murb. (Capparidaceae) occurring in southern Tunisia. In: Revue d'Ăcologie (La Terre et La Vie), tome 67, n°3, 2012. pp. 305-312
Effet de la durée de conservation, de la couleur et de la période de récolte des semences sur la germination de Diplotaxis harra (Forssk.) Boiss., plante envahissante en Tunisie méridionale
Seeds of Diplotaxis harra (Forssk.) Boiss., an invasive plant species of Southern Tunisia, were collected in July 2007, January 2008 and, April 2008 and stored under laboratory conditions. Directly after collection and each three months, germination experiments were conducted in darkness at 15°C, which corresponds to the thermal optimum for the germination of this species. The results show that seed color did not significantly affect the germination pattern of
D. harra. Seeds, notably those collected in summer, maintained a high germination rate even after 18-month storage period. These germination characterisitics could partly explain the invasive behaviour of this species.Les semences de Diplotaxis harra (Forssk.) Boiss., espĂšce envahissante de la Tunisie mĂ©ridionale, ont Ă©tĂ© rĂ©coltĂ©es en juillet 2007, janvier 2008 et avril 2008 et ensuite conservĂ©es dans les conditions ambiantes du laboratoire. Ă la rĂ©colte, et tous les trois mois, des essais de germination ont Ă©tĂ© conduits Ă lâobscuritĂ© et Ă 15°C, ce qui correspond Ă lâoptimum thermique pour la germination de cette espĂšce. Les rĂ©sultats obtenus montrent que la couleur des semences nâa pas dâeffet significatif sur les aptitudes germinatives de cette espĂšce. Les semences, notamment celles collectĂ©es en Ă©tĂ©, gardent un taux de germination trĂšs Ă©levĂ© mĂȘme aprĂšs une conservation de 18 mois. Ces aptitudes germinatives expliquent, du moins en partie, le caractĂšre envahissant de cette espĂšce.Tlig Tahar, Gorai Mustapha, Neffati Mohamed. Effet de la durĂ©e de conservation, de la couleur et de la pĂ©riode de rĂ©colte des semences sur la germination de Diplotaxis harra (Forssk.) Boiss., plante envahissante en Tunisie mĂ©ridionale. In: Ecologia mediterranea, tome 37 n°1, 2011. pp. 83-89
Ătude expĂ©rimentale de la compĂ©tition entre lâadventice Diplotaxis harra (Forssk.) Boiss. et lâorge (Hordeum vulgare var. Ardhaoui)
Interspecific competition between the weed
Diplotaxis harra (Forssk.) Boiss. and barley (Hordeum vulgare var. Ardhaoui) was studied in pots. Seeds of D. harra were sown in pots in association with the barley variety âArdhaouiâ
cultivated on a large scale in arid Tunisia. This study was conducted for varying density of weed. The results show that D. harra hasnât got a significant competitive effect on the growth parameters of barley as the dry total biomass and the maximum height. Similarly, the presence of D. harra did not significantly affect the parameters of barley yield as the number of ears / feet and the number of seeds / spike. Field barley invasions by this weed cannot be attributed to its competitive power. So rather allelopathic behavior of the species or its massive seed set that appears to play a key role in invasiveness.La compĂ©tition interspĂ©cifique entre lâadventice
Diplotaxis harra (Forssk.) Boiss. et lâorge (Hordeum vulgare var. Ardhaoui) a Ă©tĂ© Ă©tudiĂ©e en pot. Les graines de D. harra ont Ă©tĂ© semĂ©es dans des pots en association avec la variĂ©tĂ© dâorge «Ardhaoui» cultivĂ©e Ă grande Ă©chelle dans les zones arides tunisiennes. Cette Ă©tude a Ă©tĂ© conduite pour des densitĂ©s variables dâadventice. Les rĂ©sultats montrent que D. harra nâa pas un effet compĂ©titif significatif sur les paramĂštres de croissance de lâorge comme la biomasse sĂšche totale et la hauteur maximale. De la mĂȘme maniĂšre, la prĂ©sence de D. harra nâa pas significativement affectĂ© les paramĂštres du rendement de lâorge comme le nombre dâĂ©pis/pied et le nombre de graines/Ă©pi. Lâenvahissement des champs dâorge par cette adventice ne peut donc pas ĂȘtre attribuĂ© Ă son pouvoir compĂ©titif. Câest ainsi plutĂŽt le comportement allĂ©lopathique de lâespĂšce ou sa grenaison massive qui semblerait jouer un rĂŽle primordial dans son caractĂšre envahissant.Tlig Tahar, Gorai Mustapha, Neffati Mohamed. Ătude expĂ©rimentale de la compĂ©tition entre lâadventice Diplotaxis harra (Forssk.) Boiss. et lâorge (Hordeum vulgare var. Ardhaoui). In: Ecologia mediterranea, tome 38 n°1, 2012. pp. 89-95