Data collection
For each treatment, we arranged three to four times of sampling,
according to their growth stages and the lengths of life cycle, and
generally harvested them at the stages of vegetative growth, late
vegetative or early reproductive growth, and middle to late reproductive
growth respectively (Table 1). For individuals that germinated in spring
(GT1), we took an additional sample at their early vegetative growth
stage as an extra harvest (EX), as a second reference (the first one is
the vegetative growth stage) for comparison with the first samplings of
other treatments, since the plants germinated early had a prolonged
vegetative growth. At each harvest, five to six individual plants were
randomly chosen from each plot, making a maximum total of 6 replicates ×
3 blocks × 4 treatments × 3 harvests + 6 replicates × 3 blocks × 1
treatments (SP) × 1 harvest = 234 samplings. For each individual plant,
the following traits were measured (if applicable): main root length,
diameter at the basal of the main root, length and number of lateral
roots (above or equal to 1 mm in diameter along the main root), the
length of stem, diameter at the base of stem, petiole length and angle,
leaf number, lamina width (leaf size, abbreviations for all traits are
in Table 2). For individuals from GT1 and GT4 treatments, some traits
were unavailable for measurement at early growth stages due to small
plant sizes. Each plant individual was then separated into roots, stems,
petioles, laminas, reproductive modules and branches (if there were
any), oven-dried at 75oC for two days and weighed.
Reproductive modules consisted of flowers and fruits produced along the
main stem and branches, and branches included the stems and leaves on
branches. Total mass and mass allocation traits were calculated.