Juvenility and long-short day requirement in relation to flowering of Paspalum atratum in Thailand

In a study on flowering, Paspalum atratum cv. Ubon was confirmed as a long-short day plant exhibiting a quantitative response to long, days followed by a qualitative response to short days. Plants 20, 40 and 60 days of age exposed to a full period of 60 long days in a plant growth chamber (14 h light) fully flowered after being placed outside in natural shortening day-lengths. Plants that were planted as sprouted seeds in the growth chamber at the beginning of the 60 long-day period took 2-3 days for first leaves to appear and incomplete flowering (88%) resulted when they were exposed to natural shortening day-lengths. Plants that received 0, 20 and 40 long days did not flower after being exposed to natural shortening day-lengths. Plants that were not transferred outdoors but remained growing under long-day conditions in the growth chamber also did not flower. The study also confirmed that no juvenile stage exists in Ubon paspalum because all plants after being exposed to 60 long days in a growth chamber at 20, 40 and 60 days of age flowered following exposure to natural shortening day-lengths. The importance of the long-short day flowering response for agronomic management of Ubon paspalum seed crops is discussed.