<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0377-9424</journal-id>
<journal-title><![CDATA[Agronomía Costarricense]]></journal-title>
<abbrev-journal-title><![CDATA[Agron. Costarricense]]></abbrev-journal-title>
<issn>0377-9424</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Costa Rica. Colegio de Ingenieros y Agrónomos. Ministerio de Agricultura y Ganadería]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0377-94242015000200121</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Determinación de las etapas de inicio de macollamiento, inicio de primordio, floración y madurez en la planta de arroz,con el sistema s, v y r correlacionado con la sumatoria térmica]]></article-title>
<article-title xml:lang="en"><![CDATA[Determining the stages of tillering stage, initiation of primordia, flowering and maturity in the rice plant, with the system S, V and R correlated with the thermal sum at the time]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Velázquez]]></surname>
<given-names><![CDATA[Jennifer]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rosales]]></surname>
<given-names><![CDATA[Andrea]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rodríguez]]></surname>
<given-names><![CDATA[Hernán]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Salas]]></surname>
<given-names><![CDATA[Rafael]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Hacienda Mojica  ]]></institution>
<addr-line><![CDATA[Bagaces Guanacaste]]></addr-line>
<country>CR</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Universidad de Costa Rica Centro de Investigaciones Agronómicas ]]></institution>
<addr-line><![CDATA[ San José]]></addr-line>
<country>CR</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2015</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2015</year>
</pub-date>
<volume>39</volume>
<numero>2</numero>
<fpage>121</fpage>
<lpage>130</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S0377-94242015000200121&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S0377-94242015000200121&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S0377-94242015000200121&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[ResumenEn el cultivo del arroz, la temperatura es uno de los factores de clima que ejerce mayor efecto sobre el crecimiento, desarrollo y producción de la planta; la acumulación de calor constituye la energía necesaria para completar un determinado estado fenológico. Se determinó en plantas de arroz las etapas de inicio de macollamiento, inicio de primordio, floración y madurez de cosecha, empleando el sistema S, V y R, propuesto recientemente por Counce et ál. (2000), que consiste en el conteo del número de hojas completamente desarrolladas; además, se correlacionó con los grados día acumulados que la planta presentaba en ese momento, para estimar con cuántos grados día se iniciaba una etapa fenológica; este parámetro está relacionado con la temperatura promedio diaria y una temperatura base de 10ºC. Para el inicio de macollamiento la planta necesitó de 140,9 grados día; en inicio de primordio 1268,9; para floración 1746,0; y completó su ciclo con un total de 2333,2 grados día. El estudio permite concluir que, para una variedad de ciclo largo (130-135 días), cuando la acumulación de grados día sea igual o similar a los datos anteriores, la planta está iniciando una de las etapas fenológicas mencionadas; no obstante, se debe calibrar cada una de las variedades de mayor uso por el productor, debido a que entre ellas existen diferencias en duración del ciclo de cultivo.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[AbstractTemperature is one of the major climatic factors that affect growth, development and yield of the rice crop, and also can reduce the time of change of phenological stages. The beginning stages of tillering, initiation of primordia, flowering and harvest maturity were determined with the S, V and R system recently proposed by Counce et ál. (2000); it consists on counting the number of fully developed leaves; in addition, a correlation was made with accumulated degree days that the plant had at that time, in order to estimate with how many degree days the plant began a phenological stage; this parameter is related to the average daily temperature and a base temperature of 10ºC. For the start of tillering the plant needed 140.9 degree days; for primordium start, 1268.9; for bloom 1746; and completed its cycle with a total of 2333.2 degree days. This allows to conclude that, for a variety of long cycle (130-135 days), when the accumulation of degree days is equal or similar to the previous data, the plant initiates one of the above-mentioned phenological stages; however, each one of the varieties in use by farmers must be calibrated, because there are differences in crop cycle length among them.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Arroz]]></kwd>
<kwd lng="es"><![CDATA[fenología]]></kwd>
<kwd lng="es"><![CDATA[temperatura]]></kwd>
<kwd lng="es"><![CDATA[grados día]]></kwd>
<kwd lng="es"><![CDATA[macollamiento]]></kwd>
<kwd lng="es"><![CDATA[primordio]]></kwd>
<kwd lng="es"><![CDATA[número de hojas]]></kwd>
<kwd lng="en"><![CDATA[Rice]]></kwd>
<kwd lng="en"><![CDATA[phenology]]></kwd>
<kwd lng="en"><![CDATA[temperature]]></kwd>
<kwd lng="en"><![CDATA[degree day]]></kwd>
<kwd lng="en"><![CDATA[tillering]]></kwd>
<kwd lng="en"><![CDATA[primordium]]></kwd>
<kwd lng="en"><![CDATA[leaf number]]></kwd>
</kwd-group>
</article-meta>
</front><back>
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