Bangladesh J. Bot. 46(1): 517-525, 2017 (March) Supplementary GROWTH, PHYSIOLOGY AND FRUIT QUALITY OF HIBISCUS SABDARIFFA L. IN RESPONSE TO REGULATED DEFICIT IRRIGATION SITI ZAHARAH SAKIMIN * , NUR SILA AHMAD NAHAR, ABDUL SHUKOR JURAIMI, MD AMIRUL ALAM 1 AND FARZAD ASLANI Department of Crop Science, Faculy of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Keywords: Hibiscus sabdariffa, Water stress, Physiology, Fruit quality Abstract The effects of deficit irrigation technique on growth and fruit quality of roselle (Hibiscus sabdariffa L.) was observed. The result shows that minimum weight of the yield was obtained from treatment grown with well watered (WW) condition. Plant height was affected by reduction of water application. Regulated deficit irrigation (RDI) tended to decrease all means of growth parameter except stem fresh and dry weight. RDI shows significant effect on yields, where the reduction of 50% water produce more fruits compared to control plants. The impact of RDI was not significant effect on physiological change of roselle. Thus, RDI could be a feasible technique for Roselle production as it saves large amounts of water with reduction on plant growth but increase the yield as compared to well watered (WW) of roselle. Introduction Hibiscus sabdariffa L. of Malvaceae has a wide number of uses in food and as additive to foods worldwide and particularly in Malaysian (Mohd-Esa et al. 2010). Cultivation of roselle requires irrigation, but water limitation is one of the problems. For developing practical solutions to manipulate physiological response to water stress is regulated deficit irrigation (RDI). These techniques can decrease the water use (McCarthy 2002). In RDI technique, crops are allowed to sustain some degree of water deficit in order to reduce the cost and potentially increase income by reducing the cost of water (Owusu et al. 2011). Campos et al. (2009) determined partial root drying (PRD) effects to Solanum lycopersicum L. which successfully maintained the yield compared to conventional irrigation of tomato. It was, therefore hypothesized that the application of RDI may play a role in retarding plant growth, reducing physiological activity and improving fruit quality of roselle. The present work was undertaken to determine the effects of RDI on physiological change, growth and fruit quality of Hibiscus sabdariffa L. Materials and Methods The study was conducted at Field 10, Universiti Putra Malaysia. The seeds were germinated on germination tray containing peat moss as substrate. After 10 - 15 days of sowing, the seedlings were transferred 25.4 × 30.48 cm polybag. The soil mixture of planting medium was prepared by mixing top soil, coco peat and paddy husk at a ratio of 2 : 1 : 1. The polybags were placed under shade-house. Distance between plants was 1 m × 1 m. The experiment was laid down in randomized complete block design having three replications. The experiment was two factorial with irrigation (Well watered; WW and regulated deficit irrigation) and time of sampling (2, 4, 6, *Author for correspondence <sitizaharah.sakimin@gmail.com>. 2 School of Agriculture Science & Biotechnology, Faculty of Bioresources and Food Industry, Universiti Sultan Zainal Abidin, Besut Campus, Besut 22200, Terengganu, Malaysia.