RELATIONSHIP BETWEEN GROWTH REDUNDANCY AND SIZE INEQUALITY IN SPRING WHEAT POPULATIONS MULCHED WITH CLEAR PLASTIC FILM

Spring wheat (Triticum aestivum) plants normally produce tillers, many of which do not survive to produce grain-bearing spikes. Increasing the percentage of tillers that survive has hypothesized as an approach for increasing yield of wheat plants. This study was conducted to determine the effects of plastic film mulch on percentage of abortive tillers and harvesting index in two spring wheat populations, and to explore its mechanism in relation to size inequality and life-history strategies theory. Field-grown spring wheat mulched with plastic film showed a remarkable increase in grain yield (+38.5% of non-mulched control averagely), which mainly resulted from the significant increase in above ground biomass (+44.7%). At the same time, however, reproductive allocation (spike weight/above ground biomass, -5.2%) and harvesting index (-4.5%) were significantly lower (p0.05) in mulched than unmulched populations in both 2 cultivars. Meanwhile, the number and weight of barren shoot and the ratio of barren shoot biomass were significantly greater in mulched populations than unmulched controls both at booting, flowering and ripening stages. From tilling to ripening stages, the trend of G (Gini coefficient) showed obvious differences between mulched populations (∧ type with the peak of G at booting stages) and non-mulched controls (∨type with the lowest G at flowering and rebounded at ripening stage). At booting and flowering, the G was significantly higher in mulched populations than unmulched controls, and it was just contrary at ripening. Reproductive allocation and harvesting index (HI) were both negatively correlated to average G of the populations. From these results, we concluded that appreciable growth redundancy occurred in spring wheat populations mulched with plastic film may result from the exacerbated inter-plant competition and self-thinning (evidenced by increasing in the degree of Gini coefficient at booting and flowering stages). Thus, spring wheat cultivation with plastic film mulching does not always mean efficiency, although there is a remarkable increase in grain yields.