NURSE ASSOCIATION OF THE STEM SUCCULENT Caralluma acutangula IN ITS NATURAL HABITAT

Masrahi Y.S., Al-Yemeni M.N., Sayed O.H.: Nurse association of the stem succulent Caralluma acutangula in its natural habitat. Ekológia (Bratislava), Vol. 31, No. 1, p. 46- 53, 2012. The leafless perennial Caralluma acutangula is an abundant stem succulent in the arid desert of southern Saudi Arabia. The plant shows a tendency to associate with other plants growing at the study site. Work carried out to reveal the nature of this nurse association indicated that C. acutangula tends to associate with the shade provided by other plants, regardless of the plant species it associates with. Moreover, exposed C. acutangula plants growing without nurse association tend to develop stem lobes with deeply angled edges that increase turbulent airflow and increase convective heat capacity. These exposed plants also tend to develop narrower pitted xylem vessels per unit root area to decrease xylem vessel vulnerability to embolism. Results collectively indicated that C. acutangula nurse association with other plants is due to enhanced seedling establishment in shaded places, where moisture and protection from heat and high irradiance are available. Results are discussed in terms of the subtle balance that this succulent species keeps between biotic and abiotic nurse association. Key words: Caralluma acutangula, nurse association.

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