On the possibility of using a chlorophyll fluorescence parameter as an indirect indicator for the growth of Phalaenopsis seedlings

Chlorophyll fluorescence has been widely used in studies of plant physiology. The objective of this work is to seek the possibility of using a fluorescence parameter as an indirect indicator of the growth of Phalaenopsis seedlings after leaving culture vessels, so that the seedlings with impaired metabolism and growth can be screened out at an early stage. Our results showed that the initial weights and Fv/Fm ratios of seedlings measured during deflasking had nothing to do with the subsequent growth rate. Within 1–2 weeks after deflasking, the Fv/Fm ratios of most seedlings suffered a substantial drop, which might be related to the stress brought about by environment change. However, the Fv/Fm ratios of normal-growing seedlings started to rise after 3 weeks, while those of slow-growing seedlings continued to decline. It was found that the Fv/Fm values as well as their direction of change measured after the initial fluctuating period were correlated with the growth rate, and thus could be used as criteria for distinguishing between normal and slow-growing seedlings. Due to the ease of use and non-invasiveness of chlorophyll fluorescence measurement, it can be developed into a high-throughput screening tool for monitoring the growth of Phalaenopsis seedlings.