Growth and flowering of Eustoma grandiflorum as affected by artificial reduction of direct solar radiation

In order to estimate the effect of topographic shading on growth and flowering of Eustoma grandiflorumin hilly and mountainous areas, 3 early-flowering cultivars and a late-flowering cultivar were planted close to artificial sheets (3.1 m high) facing east, west, south and north in November, June and September. Total photon flux density (TPFD) on the north side of the sheet was 21% of that on the south side during winter, whereas TPFD was 94% during summer. In the November planting, plants were exposed to low TPFD on the north side just after planting and flower quality of early-flowering cultivars on the north side was better than that on the south side. In the June planting, growth of Eustoma was similar in all plots. In the September planting, when TPFD decreased after planting, growth of Eustoma on the north side was reduced in comparison with that on the other three sides. On the east and west sides, all cultivars flowered normally irrespective of planting date, and the mean values of TPFD in December and January were larger than 10 μmol m^-2 day^-1. The results indicate that high quality flowers may be produced in hilly and mountainous areas where TPFD values of 10 mol m^-2 day^-1 are ensured. (author)