The physiology of Curcuma alismatifolia Gagnep. as a basis for the improvement of ornamental production

Abstract

Distribution and morphology Curcuma is one of the largest genera in the Zingiberaceae family. This genus is in the tribe Zingibereae, which is widely distributed in tropical Asia from India to South China, Southeast Asia, Papua New Guinea and Northern Australia. Thailand seems to be one of the areas richest in this genus (Larsen and Larsen, 2006; Sirirugsa et al., 2007). Approximately 38 species of Curcuma are now found in Thailand, separated into 5 groups, i.e., 1) the “Alismatifolia” group of eight species, C. alismatifolia, C. gracillima, C. harmandii, C. parviflora, C. rhabdota, C. sparganiifolia and two new species, found in the northeastern and eastern region; 2) the “Cochinchinensis” group of two species, C. cochinchinensis and C. pierreana, distributed in the north, southwest and eastern regions; 3) the “Ecomata” group of seven species, C. bicolor, C. ecomata, C. flaviflora, C. glans, C. singularis, C. stenochila and one new species, distributed in the northern, northeastern, eastern and southeastern regions; 4) the “Longa” group of thirteen species, C. aeruginosa, C. amada, C. angustifolia, C. aromatic, C. comosa, C. latifolia, C. leucorrhiza, C. longa, C. mangga, C. rubescens, C. viridiflora, C. zanthorrhiza and C. zedoaria, found widely in the north; and 5) the “Petiolata” group of eight species, C. aurantiaca, C. petiolata, C. roscoeana, C. rubrobracteata and four new species, found from the north to the peninsula along the western ranges (Sirirugsa et al., 2007). Unlike C. longa (tumeric), C. zedoaria, C. aromatic, etc., which are species generally used as medicinal plants (Sabu and Skornickova, 2003), C. alismatifolia Gagnep. is widely cultivated as an ornamental Curcuma for cut flowers and potted plants because the attractive inflorescence has a pink coma bract, called Siam Tulip or Patumma, with a long vase life (Figure 1). This flower clone was first selected by Dr. Pisit Woraurai from Chiang Mai University, and the famous selected clone called ‘Chiangmai Pink’ was introduced as an ornamental plant in early 1980, and nowadays is wellknown in the world market (Woraurai, 1991; Department of Agricultural Extension, 1995; Wannakrairot, 1997). The aboveground organs consisted of leaves and inflorescences. There are two types of leaves, sheath leaves are former sprouting with short and thick leaf blade and followed by foliage leaves with elliptic shape, deep green and reddish median vein. Stomata is mostly tetracyctic type, however, pentacytic and hexacytic types were found in both upper and lower surfaces. Guard cells are kidney shape and the cell size in the adaxial is longer than the abaxial site. Stomatal density in the abaxial site was about 1,000–1,200 stomata mm-2 which was higher than in adaxial site (400–500 stomata mm-2). The cuticle layer of upper leaf surface is about 10–12 μm thick and thicker than the lower leaf surface (13–15 μm thick) (Anuwong et al., 2014b). Underground organs consist of two parts, i.e., the underground stem called a stubbed German Society for Horticultural Science