Interference of volunteer corn in growth and chlorophyll fluorescence of bean

ABSTRACT Corn kernels or seeds that remain after harvest can germinate and become a troublesome volunteer plant where bean crops are grown. The objective of this study was to evaluate the effect of time of emergence of volunteer corn on growth parameters, photosynthetic pigments and chlorophyll fluorescence in bean plants, competition for soil and light and light resources. The study was conducted in completely randomised experimental design, in 2×2×2+2 factorial scheme with four replications, involving two bean cultivars in competition with volunteer corn, emerging seven days before and simultaneously with beans, besides the partitioning of the competition by soil and light, just light and two controls without competition. We measured the levels of chlorophyll a, b, total and carotenoids, parameters related to chlorophyll fluorescence and bean growth variables. Volunteer corn was more competitive when it emerged seven days before the beans. When competition was established by light resource, there was a reduction in photosynthetic pigments and morphological variables of the bean plants. When competition by soil and light resources occurred, there was a reduction not only in photosynthetic pigments and morphological characteristics, but also in the chlorophyll fluorescence variables. There were significant correlations between the growth variables of the bean plants and chlorophyll fluorescence, which makes it an important analytical tool for quantifying the stress caused by weeds.

摘要 收获后残留的玉米籽粒可萌发，在大豆种植田中成为棘手的自生玉米（volunteer corn）杂草。本研究旨在探究自生玉米的出苗时间对大豆植株生长参数、光合色素及叶绿素荧光（chlorophyll fluorescence）特性的影响，以及其对土壤与光照资源的竞争效应。本试验采用完全随机试验设计（completely randomised experimental design），以2×2×2+2析因方案开展，设置4次重复。试验包含两个大豆品种，分别与早出苗7天、同期出苗的自生玉米进行竞争；同时设置三类竞争处理：土壤与光照共同竞争、仅光照竞争，以及两个无竞争对照组。本试验测定了大豆植株的叶绿素a、叶绿素b、总叶绿素、类胡萝卜素含量，叶绿素荧光相关参数及大豆生长指标。相较于同期出苗的自生玉米，早于大豆7天出苗的自生玉米竞争优势更强。当仅存在光照资源竞争时，大豆植株的光合色素含量与形态指标均出现下降。当同时存在土壤与光照资源竞争时，大豆植株不仅光合色素含量与形态特征出现下降，叶绿素荧光参数也显著降低。大豆植株生长指标与叶绿素荧光参数间存在显著相关性，这表明叶绿素荧光可作为量化杂草胁迫的重要分析工具。