Factors Affect Flower Bud Yellowing in Dendrobium Sonia ‘Ear-Sakul’

Abstract

One of the critical problems in the commercial production of Dendrobium cut-flower is preharvest un-open floret yellowing. To understand the cause of the un-open floret yellowing, the present study was aimed to determine the relationship between plant parameter as well as environmental factors that affected um-open floret yellowing in Dendrobium Sonia ‘Ear-Sakul’. The Experiment was monitored in the Orchid 2002 company, Nakhon Pathom province during November 2004 to May 2006. Monitoring un-open floret yellowing was carried out for 4 flowering stages of inflorescences namely 1) without open floret, 2) with two open florets, 3) with four open florets and 4) with six open florets per inflorescence. For each stage, 20 plants were evaluated. The relationship between plant parameters environmental factors and percentage of inflorescences with yellowed un-open floret was determined using correlation analysis. The results showed that the percentage of inflorescence with flower bud yellowing in winter was the highest of the year. The percentage of inflorescence with yellowed flower bud had positive correlation with the number flower bud per inflorescence and per pseudobulb (r=0.250 and 0.289 respectively) and negative correlation with the number of open florets per inflorescence and per pseudobulb (r=-0.238 and -0.190 respectively). The percentage of inflorescence with yellowed flower bud was found to be negative correlation with the average daytime temperature for 5 days before bud yellowing (r=-0.426) and the average daytime maximum moisture content for 5 and 7 days before flower bud yellowing (r=-0.545 and -0.588 respectively).