Effect of Watering Regimes on the Germination and Early Seedling Growth of Annona muricata

This study was carried out to determine the impact of different watering frequencies on germination and early growth of Annona muricata seeds and seedlings respectively. Three watering regimes (once in a week, twice in a week, and thrice in a week) were used. Evaluation of early seedling growth under the three watering regimes was based on height, collar diameter, and leaf number. Seed germination was significantly affected (p ≤ 0.05) by the watering regimes. Seeds watered thrice weekly had the highest germination percentage (88.6%), followed by those watered twice weekly (58.6%) and those watered once weekly (53.34%). There were also significant differences (p ≤ 0.05) in seedling height and collar diameter at all stages of growth (months 1, 2, 3 and 4) and in leaf number at months 1-3. Watering thrice a week gave the highest seedling height at months 2-4, highest seedling collar diameter at months 3-4 and highest leaf number at months 1-4 while the lowest seedling height, collar diameter and leaf number, were observed under once-in-a-week watering regime at months 1-4. These findings imply that A. muricata cannot be raised under some form of water stress condition since more frequent watering enhanced its germination and growth of seedlings. INTRODUCTION Annona muricata commonly called soursop and belonging to the family Annonaceae is a tropical fruit tree and one of the minor crops that is gaining popularity because of its economic and medicinal importance (Okoli et al., 2016). It is a native of the warmest tropical area in South and North America and is widely distributed throughout tropical and sub-tropical parts of the world including India, Malaysia, and Nigeria (Moghadamtousi et al., 2015). The species is small, slender, evergreen tree, and grows to height of 4-8m tall when mature (Pinto et al., 2005). The fruit is large, heart shaped and green in colour, ranging in diameter between 15 to 20cm (Moghadamtousi et al., 2015) and weighing up to 7kg (Orwa et al., 2009). It is a multipurpose plant with acceptable nutritional value as food products, sources of medicinal and industrial products as well as contributing directly to food security and supplementary household income for smalland medium-scale farmers (Joseph-Adekunle, 2014). Water is the physical basis of life in living organisms. It is required by plants for the manufacture of carbohydrates and as a means for transportation of foods and mineral elements (Isah et al., 2012). Water requirement in plants is dependent on the botanical characteristics of the plants, its age of growth and the prevailing weather conditions of the region (Sale, 2015) Gbadamosi (2014) stated that plant species respond differently to water availability and that different plant parts adapt differently to varying water stress conditions. Insufficient moisture below the critical level is known to cause changes in cell structure leading to the death of plants (Shinkafi and Aduradola, 2009). Water has been recognised as a determinant factor for seed germination since it can affect germination parameters in plants (Shaban, 2013). According to Doescher et al. (1985) moisture stress is one of the parameters that can influence the adaptability and regeneration success of a species population. PAT June, 2018; 14 (1): 66-72 ISSN: 0794-5213 Online copy available at www.patnsukjournal. net/currentissue Publication of Nasarawa State University, Keffi Moisture stress causes reduction in general physiological activities and thus growth and development of plants (Shinkafi and Aduradola, 2009). Isah et al. (2012) also stated that too much water in excess of plants need may retard physiological processes in plant cell. Robert and Smith (1982) assessed survival and the growth of black oak under different watering regimes and found significant difference in the regimes. Mohammed et al. (2013) reported significant effect on the growth of tropical trees under different watering regimes. This study aimed at ascertaining and recommending suitable watering regime for the germination and early seedling growth of A. muricata. It is expected that the findings will enhance the propagation and cultivation of A. muricata especially now that its nutritional and medicinal values are better appreciated. MATERIALS AND METHODS Study Area This study was carried out at the Forest Nursery of the Department of Forestry and Wildlife Management, Faculty of Agriculture, University Of Port Harcourt Nigeria between March to October 2017. The nursery site lies on Latitude 04 53' 38.3" N and longitude 00.6 54' 38" E. Collection and Processing of Seeds The fruits of A. muricata were collected from five trees at Edegberi Better-land Community in Rivers State. The seeds were processed manually and mixed properly to form a seed-lot. Seed viability test was done using the floatation method by soaking seeds in water for three hours. Seeds that sink were regarded as viable and used for the study, while the seeds that floated were discarded. Experimental Design The experiment was laid out in a completely randomized design involving 450 randomly selected seeds for the three (3) watering regimes (once in a week, twice in a week, and thrice in a week) i.e. 50 seeds x 3 replicates x 3 watering regime = 450 experimental units. Seeds were sown in germination trays measuring 17cm x 13cm x 35cm, filled with sharp sand and labelled appropriately. Seeds were germinated under a 50% light shade net. No fertilizers or bacterial and/or mycorrhizal inoculation were used. After one month of establishment, seedlings were transplanted into polypots. Prior to transplanting, the polypots which were filled with topsoil were fully watered to field capacity to maintain the moisture content of the soil. At the two leaf stage, young seedlings were transplanted into polypots measuring 15cm x 15cm x 20cm when flat. All bags were watered daily after transplanting for one month until the seedlings were properly established (considered to be seedlings with new leaves). A completely randomized design was used. Ninety (90) seedlings equally divided among three watering regimes once in a week, twice in a week, and thrice in a week (i.e. 10 seedlings x 3 watering regimes x 3 replicates = 90 experimental units) were used to determine the most appropriate watering regime for the early growth of A. muricata. Weeding was carried out regularly and when required throughout the period of the experiment. Data Collection Observation on germination was made and recorded daily for a period of sixty days. Germination percentage was calculated as: Germination percentage (GP) = x Seedling height, stem collar diameter and number of leaves were measured immediately after PAT 2018; 14 (1): 66-72 ISSN: 0794-5213; Fredrick et al ; Effect of Watering Regimes on the Germination . 67