Response of Chinese water chestnut (Eleocharis dulcis (Burm. f.) Hensch) to photoperiod

As a crop new to the western world, opportunities for production of Chinese water chestnut have barely been exploited. In China, over the latitude ran ge 21 degrees to 34 degrees N it is planted in spring and harvested in autu mn. Opportunities exist to extend its cultivation to new climates, where gr owth throughout the year is not constrained by low temperature, but may be constrained by photoperiod. To study the response of Chinese water chestnut to photoperiod, six experiments were conducted in tropical central Queensl and. One set focussed on planting early in spring, with long-day treatments superimposed. Another set investigated autumn and winter plantings, also w ith superimposed long-days, and the third compared the performance of Chine se water chestnut under constant or decreasing photoperiods, ranging from 8 h to 20 h, in light-out chambers. Corm formation was strongly retarded by long days but promoted by the photoperiods which were shorter than a critic al maximum. The critical photoperiod was between 12.0-12.5 h, below which c orm formation was rapid, and above which it was non-existent, or minimal if combined with cool (<21 degrees mean) temperature. Under short days, to th e detriment of stem growth, significantly more dry matter was allocated to corms and rhizomes. The latter provided potential corm sites. The response of corm formation and rhizome production to photoperiods shorter than the c ritical was more pronounced the more extended the treatment period. The dat a provide evidence for the ability to manipulate timing of harvest at the f ield scale to extend availability of fresh produce on the market.