رسائل ماجيستير
English
2020
Allelopathic effects of the invasive plant (Prosopis juliflora (Sw) DC) on Omani wild plants (Prosopis cineraria (L) and Vachellia tortilis)
Areej Abdulaziz Saud Al-Musalamiyah , Hassan Ali Al-Reas, Sardar A. Farooq
كلية العلوم-جامعة السلطان قابوس · عمان
Prosopis juliflora (mesquite) is an invasive plant species that poses a serious threat to agricultural lands and native floral biodiversity due to its rapid adaptability and growth under arid and semi-arid conditions. In response, the Omani government launched a national eradication campaign in 2016. One of the mechanisms driving its invasiveness is allelopathy—a biological phenomenon wherein the plant releases allelochemicals that negatively affect surrounding vegetation. However, limited information is available on the allelopathic impacts of P. juliflora on indigenous tree species, particularly under environmentally realistic concentrations of these compounds. Moreover, the responses of plants exposed to allelochemicals derived from different parts of P. juliflora (leaves and pods) vary, and the molecular interactions remain poorly understood.
This study aimed to assess the allelopathic effects of P. juliflora on two native Omani tree species—ghaf (Prosopis cineraria) and samr or acacia (Vachellia tortilis)—using aqueous extracts and powdered forms of leaves and pods. Seeds of both species were exposed to relatively low levels of plant material (0.5% and 5.0% w/w powders; 10 and 100 mg/L aqueous extracts), then grown in a 1:1 mixture of sandy soil and compost. Seedling development was monitored over 28 days post-germination.
Results showed that seed germination rates and growth parameters (root length and seedling biomass) were not significantly affected by the presence of P. juliflora extracts or powders. However, V. tortilis seedlings exhibited increased chlorophyll a and b content, especially under pod treatments, whereas P. cineraria seedlings showed no significant changes in these pigments. In contrast, carotenoid content increased in P. cineraria seedlings exposed to extracts but decreased under powder treatments. No significant effects on carotenoids were observed in V. tortilis. Additionally, exposure to P. juliflora powders led to elevated proline levels in P. cineraria seedlings—an indication of stress—while V. tortilis seedlings remained unaffected.
These findings suggest that the relatively low concentrations of P. juliflora allelochemicals used in this study do not significantly inhibit fundamental physiological processes such as mitotic division and root elongation in the tested species. Nonetheless, the effects were generally more pronounced with powders than with aqueous extracts. Overall, the laboratory experiments revealed limited allelopathic impact of P. juliflora on the two native species, although further research using field-collected soils—particularly from areas under or near the canopy of P. juliflora—is recommended, as natural leaf litter accumulation may influence plant interactions more strongly in situ.