A Study on early vigor of rice genotypes under low-input culture

本研究旨在(1)评估不同水稻基因型早活力的变异；(2)鉴定导致早活力差异的植物性状；(3)评估早活力在作物生产过程中的意义。本研究从粳稻、热带粳稻和籼稻的改良品种和地方品种中选择了63个不同的基因型。对4个品种在水培条件下进行了深入观察，对幼苗干物质生长进行了分析，将其定义为异养生长（种子储备利用率DW_h）和光合作用自养生长（DW_a）之和。DW_h的时间变化过程可以用logistic函数很好地描述，其中DW_<hMax>是生长速率的主要决定因素，而DW_a的变化则可以用指数函数来表示，RGR是各基因型的主要参数。早壮变异：63个基因型的幼苗生长至分蘖开始在190 ~ 590mg/pl范围内变化。上述公式很好地反映了它们的生长和DW_<hMax>， RGR分别为9 ~ 22mg和8.6 ~ 11.4mg g^<-1>（°Cd^<-1>）。通过敏感性分析，证明了早熟活力的变异更多地依赖于自养生长而不是异养生长。异养活性决定因子RGR与干物质向地上植物各器官的分配呈正相关。田间条件下与杂草竞争的早期活力的意义在有和没有紫霉作为竞争对手的情况下，田间种植了4个对照品种。从生育期开始，竞争对水稻生长有明显的影响。在此期间，早期活力较强的品种的DW降低率较小。

This study was conducted to (1) evaluated variability of early vigor among divergent rice genotypes, (2) identify plant traits that cause differential early vigor, and (3) evaluate the significance for early vigor in the crop production processes. Divergent 63 genotypes were chosen for this study from improved and local cultivars of japonica, tropical japonica and indica.1. Growth analysis of seedling growthAn intensive observation of the four cultivars was conducted under hydroponic culture and dry matter growth of seedlings was analyzed defining it the sum of heterotrophic growth (utilization of seed reserve, DW_h) and autotrophic growth based on photosynthesis (DW_a). The time course of DW_h was well described with a logisticfunction with DW_<hMax> as a primary determinant of growth rate, while the change in DW_a was represented by an exponential function with RGR as a primary parameter for each genotype.2. Variability of early vigorThe seedling growth to beginning of tillering varied among 63 genotypes from 190 to 590mg/pl. The above formula well represented their growth and DW_<hMax>, and RGR varied 9 to 22mg and 8.6 to 11.4mg g^<-1> (°Cd^<-1>), respectively. From a sensitive analysis, it was proved that variation of early vigor was more dependent on autotrophic than heterotrophic growth. RGR (determinant of heterotrophic activity) tended to positively correlate with the partitioning of dry matter to the aerial plant organs.3. Significance of early vigor in competition with weed under field conditionFour contrasting cultivars were grown in the field with and without E.oyzicola as a competitor. Rice growth was evidently affected by competition from early growing period. During this period, the ratio reduction of DW was smaller in the cultivars that had superior early vigor.