关键词: 石灰性褐土, 秸秆还田, 隔年深松, 深翻, 连年旋耕, 磷脂脂肪酸, 土壤酶活性

Abstract: Pollination ecological characteristics of pokeweed (Phytolacca americana) were systematically studied by measuring flowering phenology, flower quantitative characters, pollen vitality and histochemistry, stigma receptivity, pollen germination on stigmata, outcrossing index, pollenovule ratio, pollinators, and mating system. The aim of this study is to understand the mechanism underlying successful invasion of pokeweed. The results showed that the flowering span of pokeweed was 45-70 d. The life span of single flowers was 2-3 d, including goblet flowering, petal flattening, petal sagging and petal rewinding stage. The corolla was no larger than 1 cm in diameter in petal sagging stage. The distance between the anther and the stigma was 1-2.5 mm, promoting selfpollination. There was a significant difference in pollen viability between petal flattening stage and petal sagging stage (P<0.05), and no significant difference between goblet flowering stage and petal flattening stage (P>0.05). The pollen viability during petal flattening stage was higher than 85%. In the petal flattening stage, the stigma receptivity was the highest and the synthetic stigmata cracked into 9 to 10, which increased the surface area of stigma for receiving more pollen. Results from the scanning electron microscope revealed that pollen had been germinated on the stigma of this stage. Therefore, the timing of anther loose pollen coincided with the timing of synthetic stigma cracking, which might be beneficial to selfpollination. Each flower contained 1667-3222 pollen grains and 9-10 ovules. The pollen ovule ratio (P/O) was 340.88±34.99 and hybridization index (OCI) was 3. The P/O ratio suggests that pokeweed is facultative autogamous. Pokeweed has fatcontaining pollen. At least four different species of insect taxa, such as bees, wasps, scorpion flies, and thinwax bees, were the “principal pollinators”. In conclusion, pokeweed is selfcompatible with high pollen viability and strong stigma receptivity. The cooccurrence of high pollen viability and strong stigma receptivity is conducive to improve fruit setting. Those reproductive mechanism and pollination characteristics are the main factors for the successful invasion of pokeweed.

Key words: calcareous cinnamon soil, corn straw returned to soil, subsoil tillage per 2 years, convention tillage, rotary tillage every year, phospholipid fatty acid (PLFA), soil enzyme activities.