Abstract
The culture of watermelon develops mainly under conditions of high temperature, being the temperature an element that directly affects the emission of vegetative and reproductive organs. There are no reports of the accumulation of temperature required for emission of branches, nodes and flowers. Thus, this experiment aimed to evaluate the rate of emission of vegetative and reproductive organs for hybrids of watermelon in relation to air temperature, using the hybrids of Manchester and Top Gun watermelons. The experiment was conducted in Federal University of Santa Maria, campus Frederico Westphalen-RS, from September to December 2014. Evaluations were conducted at every two days and it was determined the variables: nodes emission, final number of nodes on the main stem, number of primary and secondary ramifications and number of staminate flowers and open pistillate flowers related to accumulated thermal sum for the emission of such organs, and the ratio between the number of staminate flowers to the pistillate. The hybrids of watermelon present for plastochron of 18.8 °C node day, final number of nodes of the main ramification of 43 and number of primary and secondary ramifications of eight and 20, respectively. For the emission of staminate and pistillate flowers the hybrids need an accumulation 10.5 and 46.7 °C day, respectively. The number of staminate and pistillate flowers is 52 and nine, respectively, and the ration between flowers of 6.6:1.
Highlights
According to FAO (Food and Agriculture Organization), the largest watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] production is concentrated in China, accounting for 71% of the world production, followed by Turkey, Iran and Brazil
The measurement of air temperature effect is an important tool used to estimate the period of plant development, through the accumulation of thermal units or degree-days above the base temperature estimated for the culture in jas.ccsenet.org Journal of Agricultural Science
According to the analysis of variance the variables plastochron, final number of nodes in the main stem and accumulated thermal sum showed no significance for the evaluated hybrids, by the F test at 5% probability of error (Figure 2)
Summary
According to FAO (Food and Agriculture Organization), the largest watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] production is concentrated in China, accounting for 71% of the world production, followed by Turkey, Iran and Brazil. In Brazil, the watermelon culture presented an average production of 2 million tons in 2014 (FAOSTAT, 2015) and has an important social role, being responsible for a large number of jobs, especially in the south, southeast, northeast and midwest regions (Souza et al, 2012). One of the factors that most influence the cultivation is the air temperature, since it interferes directly in the plant development (Buozo & Kuchen, 2012). The measurement of air temperature effect is an important tool used to estimate the period of plant development, through the accumulation of thermal units or degree-days above the base temperature estimated for the culture in jas.ccsenet.org
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