Shading was conducted in net-houses (2.5 m
high, 3 m long and 2 m wide) covered with one or two layers of
commercial black shading net. Each treatment involved 20 pots,
each containing five plants of heightw0.25 m. Diurnal variations of
photosynthetically active radiation (wavelength 400e700 nm)
under full sunlight and all shade treatments were measured with
a quantum sensor (TES-1332A, TES, Taipei, Taiwan), and is displayed
in Fig. 1. All plants were kept well-irrigated and protected
from bacterial pathogens and weed competition.