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

本研究的目的是（1）评价不同水稻基因型之间早期活力的变异性，（2）鉴定引起早期活力差异的植物性状，（3）评价早期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筛选出63个不同的基因型.幼苗生长分析在水培条件下对4个品种的幼苗进行了详细的观察，并对幼苗的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）和基于光合作用的自养生长（DW_a）之和。DW_h的时间进程可用logisticfunction来描述，DW<hMax>_a的变化可用指数函数来描述，RGR是各基因型生长速率的主要参数. 63个基因型的苗期生长至分蘖开始的变异范围为190 ~ 590 mg/pl。上述公式较好地反映了它们的生长和干重<hMax>，相对生长率分别为9 ~ 22 mg·g ~（-1）和8.6 ~ 11.4mg·g ~<-1>（-1<-1>）。敏感性分析表明，早期活力的变化更多地依赖于自养生长而不是异养生长。RGR（determinant of heterotrophic activity）与干物质向地上器官的分配呈正相关.田间条件下早期活力在与杂草竞争中的意义四个对照品种在有和没有E.oyzicola作为竞争对手的田间种植。水稻生长明显受到来自生育前期的竞争影响。在此期间，上级活力较强的品种，干重下降的比例较小。

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.