S05 - Session P2 - Night water cooling temperatures suppress growth, development and nitrate reductase enzyme activity in sacred lotus (Nelumbo nucifera Naertn.)

Authors: Panupon Hongpakdee *, Sornnarin Suangto, Ubon Tangkawanit, Chaiartid Inkham, Soraya Ruamrungsri

In Thailand, normal growth and flower quality of Sacred lotus was still limited by low temperature condition in mild winter. This might partially be an obstacle to promote this exotic aqua-geophyte as year round cut flower. To clarify the effects of night water cooling temperature (WCT) on its growth, the experiment was conducted in completely randomized design; CRD with 3 different water temperatures by chilling unit i.e. T1: ambient water temperature (control), T2: WCT 20 o C, and T3: WCT 15 o C under the natural condition for 2 months in greenhouse. Each cutting stolon were planted for reach 3 up-right leaves growing stage in plastic pot contained with commercial clay as substrate media, prior to transfer in 3m x 5m concrete tank filled to 3/4 of the container level with tap water after planting. Then, all plants were continuing to receive water cooling condition for 12h overnight. All decreased WCT at night suppress some aboveground growth in terms of leaf number, total leaf area and fresh weight. However, opposite result for underground growth was found as reduced WCT gave accelerate increased yields of sacred lotus rhizomes (total stolon length, quantities of total node and internode number). Water cooling temperature at 15 o C gave the lowest nitrate reductase enzyme activity associated with nitrogen assimilation. No flowering was observed under each WTC conditions during the experimental periods. This finding might confirm the role of low temperature for inducing rhizome dormancy, resulted in poor growth and flower quality of off-season sacred lotus production.