EvoluÃÃo das caracterÃsticas morfoanatÃmicas nos ciclos de seleÃÃo do milho âSaracuraâ sob encharcamento intermitente / Evolution of morpho-anatomicals characteristics on selection cycles of maize (Zea mays L.) âSaracuraâ â BRS â 4154 under intermittent soil flooding

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Although every single plant needs a certain amount of water, the excess around roots can cause severe injuries and even death of most crops. Soil flooding is one of the most important factors which affects maize crop production and development on tropical and subtropical regions. Excess of water blocks the oxygen transfer and others gases from soil to atmosphere. In Brazil around 33 millions of hectares are found under intermittent soil flooding. Even though maize is sensitive to flooding, some research has shown a great genetic variability to this condition, which places this crop as an option to grow in these areas. The sensitivity of maize to soil flooding resulted in a study carried out by Embrapa Maize and Sorghum Research Center, located at Sete Lagoas, which ended with a release of a maize variety known as âSaracuraâ which is tolerant to those conditions. The âSaracuraâ maize was subjected to 18 cycles of stratified mass selection under soil flooding. Three experiments were carried out with the objective of studying morphological and anatomical characteristics on the 18 selection cycles, searching to understand better the mechanisms involved on the greater tolerance observed on the last cycles. One trial was carried out in greenhouse conditions, where the root morphological characteristics were evaluated through a digital image program (WinRHIZO). Flooding was imposed right after plant emergence. Two other trials were carried at field conditions, with the objective of characterizing root and leaf anatomical modifications. Here, flooding started at V6 growth stage by receiving 20 cm of water three times a week. In all experiments the genetic material used were the selection cycles, C1 up to C18 (alternated) companing with control BR 107. The experimental design was a randomized complete block. The results showed that the last selection cycles presented morphological and anatomical characteristics which favors plant survive in flooded environments. There were observed in these cycles very fine roots, large length, greater total volume and superficial area. Besides that there was a greater aerenchyma formation, decrease of exoderme, modification in cortex and vascular bundles, which may facilitates flux of photosynthates and water through plants. In the leaf there was also alterations with greater amount of stomata with better function, decrease of cuticle and epidermis, decrease also on the number and size of bulliform cells, metaxylem with shorter diameter, increase in phloem thickness and shorter sclerencyma area.

ASSUNTO(S)

aerÃnquimas aerenchyma fisiologia de plantas cultivadas root anatomy hipoxia ciclos de seleÃÃo. flooding alagamento zea mays l. selection cycles hypoxia zea may l.

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