Éxito en la reintroducción en la Reserva Natural de Oued Dekouk, Túnez, de una planta autóctona, Periploca angustifolia

The study evaluates the regeneration success of an autochthonous plant species, Periploca angustifolia Labill. (periploque), using spontaneous (pre-existing) and transplanted (re-introduced from a nursery) plants in the Natural Reserve of Oued Dekouk, southern Tunisia. We compared the growth status of both types of shrubs using morphological and ecophysiological parameters. The results show that spontaneous periploque was more vigorous and appears more adapted to aridity than transplanted periploque. Indeed, spontaneous shrubs have higher growth rates than transplanted ones. They also had higher leaf water potentials, indicating excellent plant water status recovery, and elevated photosynthetic assimilation rate. The better growth of spontaneous shrubs seems to be due to the efficacy of its aridity adaptive mechanisms. They limit water loss through a low leaf area and stomatal density and an efficient stomatal function. Furthermore, spontaneous plants have an efficient water-conducting system less vulnerable to embolism. Transplanted plants may have a less developed root system limiting their ability to absorb soil moisture. The present study indicates that the re-establishment of endangered plant species into areas with limited rainfall maybe more feasible by direct seeding or self regeneration, despite its slowness, than by the hardy and costly transplantation-technique.El estudio evaluó el éxito en la regeneración de una planta autóctona, Periploca angustifolia Labill. (cornical), introducida por la técnica de transplante en la Reserva Natural de Oued Dekouk (sur de Túnez), con un clima mediterráneo supra sahariano. Se llevó a cabo un estudio comparativo entre arbustos espontáneos (pre-existentes) y transplantados (a partir de un vivero) y se midieron varios parámetros morfológicos y ecofisiológicos. Los resultados muestran que los cornicales espontáneos fueron más vigorosos y están mejor adaptados a la aridez que los transplantados. De hecho, los arbustos espontáneos tienen mayores ratios de crecimiento que los transplantados. También mostraron mayor potencial hídrico en las hojas, lo que indica una excelente recuperación del estatus hídrico en la planta, y una elevada tasa de asimilación fotosintética. El mejor crecimiento de los cornicales espontáneos parece ser debido a la eficacia de sus mecanismos de adaptación a la aridez: limitan las pérdidas de agua mediante una menor área de la hoja y de densidad de estomas y una eficiente función de estos. Además, las plantas espontáneas tienen un sistema de conducción de agua eficiente menos vulnerable a la embolia. Las plantas transplantadas pueden tener un sistema de raíces menos desarrollado que limite su capacidad para absorber la humedad del suelo. El presente trabajo indica que la reintroducción de especies en peligro de extinción en áreas con precipitaciones limitadas puede ser  más viable por siembra directa o por auto-regeneración, a pesar de su lentitud, que por la dura y costosa técnica del transplante

Re-introduction success of an autochthonous plant species, Periploca angustifolia, in the Natural Reserve of Oued Dekouk, Tunisia

The study evaluates the regeneration success of an autochthonous plant species, Periploca angustifolia Labill. (periploque), using spontaneous (pre-existing) and transplanted (re-introduced from a nursery) plants in the Natural Reserve of Oued Dekouk, southern Tunisia. We compared the growth status of both types of shrubs using morphological and ecophysiological parameters. The results show that spontaneous periploque was more vigorous and appears more adapted to aridity than transplanted periploque. Indeed, spontaneous shrubs have higher growth rates than transplanted ones. They also had higher leaf water potentials, indicating excellent plant water status recovery, and elevated photosynthetic assimilation rate. The better growth of spontaneous shrubs seems to be due to the efficacy of its aridity adaptive mechanisms. They limit water loss through a low leaf area and stomatal density and an efficient stomatal function. Furthermore, spontaneous plants have an efficient water-conducting system less vulnerable to embolism. Transplanted plants may have a less developed root system limiting their ability to absorb soil moisture. The present study indicates that the re-establishment of endangered plant species into areas with limited rainfall maybe more feasible by direct seeding or self regeneration, despite its slowness, than by the hardy and costly transplantation-technique.El estudio evaluó el éxito en la regeneración de una planta autóctona, Periploca angustifolia Labill. (cornical), introducida por la técnica de transplante en la Reserva Natural de Oued Dekouk (sur de Túnez), con un clima mediterráneo supra sahariano. Se llevó a cabo un estudio comparativo entre arbustos espontáneos (pre-existentes) y transplantados (a partir de un vivero) y se midieron varios parámetros morfológicos y ecofisiológicos. Los resultados muestran que los cornicales espontáneos fueron más vigorosos y están mejor adaptados a la aridez que los transplantados. De hecho, los arbustos espontáneos tienen mayores ratios de crecimiento que los transplantados. También mostraron mayor potencial hídrico en las hojas, lo que indica una excelente recuperación del estatus hídrico en la planta, y una elevada tasa de asimilación fotosintética. El mejor crecimiento de los cornicales espontáneos parece ser debido a la eficacia de sus mecanismos de adaptación a la aridez: limitan las pérdidas de agua mediante una menor área de la hoja y de densidad de estomas y una eficiente función de estos. Además, las plantas espontáneas tienen un sistema de conducción de agua eficiente menos vulnerable a la embolia. Las plantas transplantadas pueden tener un sistema de raíces menos desarrollado que limite su capacidad para absorber la humedad del suelo. El presente trabajo indica que la reintroducción de especies en peligro de extinción en áreas con precipitaciones limitadas puede ser más viable por siembra directa o por auto-regeneración, a pesar de su lentitud, que por la dura y costosa técnica del transplante

Re-introduction success of an autochthonous plant species, Periploca angusttfolia, in the Natural Reserve of Oued Dekouk, Tunisia

The study evaluates the regeneration success of an autochthonous plant species, Periploca angustifolia Labill. (periploque), using spontaneous (pre-existing) and transplanted (re-introduced from a nursery) plants in the Natural Reserve of Oued Dekouk, southern Tunisia. We compared the growth status of both types of shrubs using morphological and ecophysiological parameters. The results show that spontaneous periploque was more vigorous and appears more adapted to aridity than transplanted periploque. Indeed, spontaneous shrubs have higher growth rates than transplanted ones. They also had higher leaf water potentials, indicating excellent plant water status recovery, and elevated photosynthetic assimilation rate. The better growth of spontaneous shrubs seems to be due to the efficacy of its aridity adaptive mechanisms. They limit water loss through a low leaf area and stomatal density and an efficient stomatal function. Furthermore, spontaneous plants have an efficient water-conducting system less vulnerable to embolism. Transplanted plants may have a less developed root system limiting their ability to absorb soil moisture. The present study indicates that the re-establishment of endangered plant species into areas with limited rainfall maybe more feasible by direct seeding or self regeneration, despite its slowness, than by the hardy and costly transplantation-technique

Water relations and drought-induced embolism in olive (Olea europaea) varieties 'Meski' and 'Chemlali' during severe drought

We examined the effects of drought on the water relations, osmotic adjustment and xylem vulnerability to embolism of olive (Olea europaea L.) varieties, 'Meski' and 'Chemlali'. Two-year-old self-rooted cuttings growing in sand-filled pots in a greenhouse were subjected to water stress by withholding water for 60 days. Water relations and gas exchange measurements showed that 'Chemlali' was more drought resistant than 'Meski' and had a greater capacity for osmotic adjustment through solute accumulation. However, when water stress was acute, the effect of osmoregulation on leaf cell turgor was largely counteracted by xylem cavitation. Cavitation vulnerability curves showed that both varieties were highly resistant to embolism formation. The xylem water potential inducing 50% loss of stem conductivity approached -7 MPa in 'Meski' and only slightly less in 'Chemlali'. Although the difference between varieties in susceptibility to xylem embolism was small, it appears to account in large part for the difference between them in the ability to tolerate severe drought

Impact of water deficit on physiological parameters, bioactive content and antioxidant activity of three olive cultivars

We studied changes in morphology, sclerophylly, chlorophyll photosynthetic parameters and total phenol contents in leaves of three olive (Olea europaea L.) cultivars; Oueslati, Jarboui and Meski which grew under water deficit conditions. Our results showed significant differences in trichome and stomatal densities, area of the leaf and relative surface of stomatal pores. The photosynthetic parameters Fv/Fm, ΦPSII and ETR were negatively affected by the water deficit in these three varieties. The total phenolic and flavonoid contents increased in all cultivars, with Oueslati showing the highest values. The Oueslati variety could be considered as the most drought-tolerant compared to Jarboui and Meski. Therefore we believe this cultivar is the most suitable for cultivation in semi-arid environments