What did the early experiments on photoperiodism demonstrate?

Question

What did the early experiments on photoperiodism demonstrate?

Answer 1

Early experiments on photoperiodism dealed with the flowering period of plants. They defined  short-day ( late summer and fall, less than about 16 hours ), long-day ( summer, longer than 9 to 16 hours ), day-neutral ( any length ), and intermediate-day ( not classifiable as either long-day or short-day)  plants in relation to their photoperiod.

One of early publications:

Factors Controlling Flowering of the Chrysanthemum: I. THE EFFECTS OF PHOTOPERIOD...

SCHWABE J. Exp. Bot..1950

Very early studies ( from the start in 18th century ) in photoperiodism you find on this site, page 87 et seq.:

http://books.google.de/books?id=u-661AIZ...

Other photoperiodic responses involving the phytochrome system include seed germination and the early growth of seedlings.