Arbutus andrachne

Abstract: The UV-absorbing capacity (measured as A(310) cm(-2) and A(365) cm(-2) or AUVR cm(-2)) of the shade leaves of four representative evergreen sclerophylls of the Mediterranean region (Quercus coccifera, Q. ilex, Arbutus andrachne and A. unedo) was considerably lower than the corresponding one of sun leaves of the same species. However, fibre optic microprobe measurements showed that adaxial as well as abaxial epidermis of shade leaves of all examined plants, except abaxial epidermis of A. andrachne, were almost as effective as the corresponding ones of the sun leaves in screening out most of the incident UV-B radiation. There is probably a threshold, under which the concentration of the UV-B absorbing compounds in the protective tissues is not furthermore reduced, in spite of the low levels of the stress factor (UV-B radiation) in the environment. On the other hand, the ability of both abaxial and adaxial epidermis to attenuate UV-A radiation, except of adaxial leaf epidermis of Quercus species, depended on the UV absorbing capacity of the whole-leaf extracts, with different correlation patterns between the two Quercus species and the two Arbutus species. This could be explained by the fact that shade leaves showed not only quantitative, but also qualitative differences (higher A(310)/A(365) ratio) in the absorbance of their methanolic extracts compared to these of sun leaves. The results of the present study showed that we should not always correlate the depth of penetration of UV radiation into sun and shade leaves according to the corresponding UV absorbing capacity of the whole leaf methanolic extracts, without taking into account all the anatomical, developmental and biochemical (such as different composition and distribution of the UV-absorbing compounds among the different protective tissues) peculiarities of the leaves of each species. (Less)

Abstract: To break dormancy and allow germination of Arbutus andrachne L. (Eastern Strawberry tree) seeds, various methods were tested including scarification with hot water, sulphuric acid (H 2 SO 4 ), or potassium hydroxide (KOH), cold moist stratification and treatment of seeds with potassium nitrate (KNO 3 ), thiourea, or gibberellic acid (GA 3 ). None of the seeds in the control or those scarified with H 2 SO 2 or KOH, or treated with KNO 3 or thiourea germinated. Hot water scarification allowed some germination, the greatest being 36% when seeds were soaked in water at 60°C for three minutes. Stratification of seeds at 4°C for three to four months or treatment of seeds with 250 mg/liter GA, was successful as 86% of the seeds germinated for both treatments.

Abstract: Stem cuttings of Arbutus andrachne L. were taken from basal or terminal portions of branches in October and treated with acid or salt forms of IBA or NAA at several concentrations. Also, the effects of wounding and propagation medium were assessed. Auxin was necessary for root formation, IBA acid being most effective. In general, salt forms of IBA and NAA were less effective than acid forms. Concentration of auxin had a significant effect on rooting regardless of auxin type or chemical form. The greatest rooting percentage, root number, length, and fresh and dry weights were exhibited by basal cuttings treated with 24 m M IBA. Position of the cutting on the branch did not affect rooting except when the IBA acid form was used; basal cuttings were then superior to terminal ones. Wounding, by making two opposite longitudinal incisions at the base of the cutting, increased rooting. The propagation medium had a significant effect on adventitious root formation, which was enhanced with increasing perlite percentage in the medium up to 100%. Chemical names used:1H-indole-3-butyric acid (IBA); α - naphthaleneacetic acid (NAA). Arbutus andrachne is an evergreen tree found in pine and evergreen oak forests in Jordan (Al-Tellawi, 1989). This tree has po- tential use as a landscape plant because of its ornamental features, which include twisted stems and branches, leathery evergreen foli- age, ornamental flowers, decorative fruits, and peeling reddish-brown bark. To introduce this plant into the landscape industry, a feasible propagation method should be developed. Propagation of Arbutus menziesii Pursh. (Hartmann et al., 1990) and Arbutus unedo L. (Stuart, 1979) by stem cuttings is documented. However, to our knowledge, no work has been done on propagation of A. andrachne by stem cuttings. Therefore, the objective of this study was to determine the influence of type, chemi- cal formulation, and concentration of auxin on rooting of A. andrachne stem cuttings taken from two branch positions. The effects of wounding of cutting bases and propagation medium on rooting were also assessed.