Methods of Enhancing Germination of Anacua Seeds

Abstract

Seed dormancy hampers establishment of anacua [Ehretia anacua (Teran & Berl.) I.M. Johnst.] in plantings for wildlife. We evaluated methods of enhancing anacua germination and causes of dormancy. Seeds were (1) scarified with 2.9 mol liter -' H202 or 0.71 mol liter' NaOCl for 10, 20, or 30 minutes, or concentrated (18.0 mol liter-) H2SO4 for 15, 30, 60, or 120 minutes; (2) rinsed with water for 12, 241 36, and 48 hours; (3) treated with 0.1, 1.4, 2.9, and 4.3 mmol liter' gibberellic acid (GA); (4) treated with 0.02 mol liter-' KNO3; (5) treated with dry heat (1300 C) for 3, 6,9, 12, and 15 minutes, (6) mechanically scarified; and (7) moist prechilled at 3 and 70 C for 2 or 4 weeks. Seeds were germinated in controlled environment chambers at 300 C. Germination was not enhanced by chemical scarification or rinsing. GA (1.4 mmol liter-) increased germination from 35% for controls to 61%. Mechanical scarification and dry heat enhanced germination of highly dormant seeds only. A 2-week moist prechill at 30 C increased germination of intact seeds from 6% for controls to 36%. Percent and rate of germination were similar among seed sources. Apparent afterripening requirements limited germination at 2 months after harvest to 3%. This requirement gradually broke down until at 8 months after harvest, germination had increased to 40%o. Our results indicated that treatment with 1.4 mmol liter-' GA or higher concentrations, moist prechilling for 2 weeks at 30 C, and storage for 8 months will increase germination of dormant anacua seeds. Authors are faculty researcher and research fellow, Caesar Kleberg Wildlife Research Institute, Campus Box 218, Texas AI and area manager, Las Palomas Wildlife Management Area, Texas Parks and Wildlife Department, 4200 Smith School Road, Austin, Texas 78744. Research was funded by the Texas Parks and Wildlife Department and The Caesar Kleberg Foundation for Wildlife Conservation. Authors wish to thank Dr. R. Bingham for his assistance in statistical analyses. Manuscript accepted 16 December 1985. Anacua [Ehretia anacua (Teran & Berl.) I.M. Johnst.] is a native, semievergreen shrub or small tree of the Boraginaceae that occurs in river valleys and bottomlands in central and south Texas southward into Mexico (Vines 1960, Correll and Johnston 1970). Anacua fruits are eaten by many birds and mammals (Vines 1960), and it is highly favored as a nest site by white-winged doves (Zenaida asiatica L.) (Brown et al. 1977). About 95% of the original brushland of the Lower Rio Grande Valley has been lost to cultivation and other land use practices. State and federal wildlife agencies are attempting to restore habitat for white-winged doves and other wildlife on former cropland in this region. Anacua is one of five woody plants considered to be of primary importance in habitat restoration. Other important species include spiny hackberry (Celtis pallida Torr.), bluewood (Condalia obovata Hook.), huisache [Acacia farnesiana (L.) Willd.], and Texas ebony [Pithecellobium flexicaule (Benth.) Coult.]. Low germination resulting from seed dormancy has hampered efforts to establish anacua. Alaniz and Everitt (1980) reported that the optimum temperature for anacua germination is 300 C. Seeds had to be soaked for 2 hours in concentrated sulfuric acid for appreciable germination to occur. Objectives of this study were to determine (1) additional methods of enhancing germination of anacua seeds and (2) possible causes of seed dormancy.