Luiz Edson Mota de Oliveira

Flooding tolerance and cell wall alterations in maize mesocotyl during hypoxia

Abstract€Œ€This research aimed to characterize the tolerance to flooding and alterations in pectic andhemicellulose fractions from mesocotyl of maize tolerant to flooding when submitted to hypoxia.In order to characterize tolerance seeds from maize cultivars Saracura BRS-4154 and BR€107 tolerantand sensitive to low oxygen levels, respectively, were set to germinate. Plantlet survival was evaluatedduring five days after having been submitted to hypoxia. After fractionation with ammonium oxalate0.5% (w/v) and KOH 2M and 4M, Saracura BRS-4154 cell wall was obtained from mesocotyl seg-ments with different damage intensities caused by oxygen deficiency exposure. The cell wall fractionswere analyzed by gel filtration and gas chromatography, and also by Infrared Spectrum with FourrierTransformation (FTIR). The hypoxia period lasting three days or longer caused cell lysis and in ad-vanced stages plant death. The gelic profile from pectic, hemicellulose 2M and 4M fractions fromsamples with translucid and constriction zone showed the appearance of low molecular weight com-pounds, similar to glucose. The main neutral sugars in pectic and hemicellulose fractions were arabi-nose, xilose and mannose. The FTIR spectrum showed a gradual decrease in pectic substances frommesocotyl with normal to translucid and constriction appearance respectively.Index terms: pectic substances, hemicellulose.Tolerância ao alagamento e alteracies de parede celular em mesocotilo de milho durante hipoxiaResumo€Œ€Objetivou-se caracterizar a tolerância ao alagamento e alteracies nas fracies pOcticas ehemicelulosicas de mesocotilos de milho submetidos a hipoxia. Sementes de milho cultivar SaracuraBRS-4154 e BR€107, tolerante e sensivel a hipoxia, respectivamente, foram submetidas a germinacaoe a sobrevivŒncia das plântulas em condicies de hipoxia, foi avaliada durante cinco dias. O€material deparede celular, obtido de segmentos de mesocotilos da cultivar Saracura BRS-4154 com diferentesintensidades de danos causados por hipoxia, foi submetido a fracionamento com oxalato de amonio0,5% e KOH 2M e€4M. As€fracies de parede celular obtidas foram analisadas por cromatografia emgel, cromatografia gasosa e espectro de infravermelho com transformacao dos dados pela sOrie deFourrier (FTIR). Periodos de hipoxia superiores a trŒs dias causaram a lise celular (aparŒncia translœcida),e, em estAEdios mais avancados, a morte das plantas. O€perfil gOlico das fracies pOcticas, hemicelulose2M e 4M das amostras de mesocotilos translœcidos e com constricao apresentaram compostos de bai-xos pesos moleculares semelhantes a glicose. Os€principais acœcares neutros nas fracies pOcticas ehemicelulosicas foram arabinose, xilose e manose. O€espectro de FTIR mostrou um decrOscimo gradu-al nas substâncias pOcticas do mesocotilo com aparŒncia normal, para translœcido e constricao respec-tivamente.Termos para indexacao: substâncias pOcticas, hemicelulose.

Anatomical characteristics and enzymes of the sucrose metabolism and their relationship with latex yield in the rubber tree (Hevea brasiliensis Muell. Arg.)

Rubber production is dependent on the availability of carbohydrates in the tissues engaged in latex synthesis. In this study three rubber tree clones were used to study the protein profile, the activities of invertase and sucrose synthase in the latex and anatomical characteristics of the bark, as well as to establish a possible relationship with latex production. The clones used in the study, RRIM 600, GT 1 and Fx2261, differed in latex productivity, from high to low in this order. Although present, few differences were observed in the latex protein profile obtained by denaturing electrophoresis. The activity of neutral invertase was higher than the acidic isoform, and both activities were higher in the most productive clones RRIM 600 and GT 1. The same was observed for sucrose synthase but it is suggested that invertase may play a more important role in sucrose cleavage in the latex. The anatomical measurements showed that the number of lactiferous cells and lactiferous rings per mm2, and lactiferous cell diameter were higher only in the most productive clone RRIM 600. Together, invertase activity and anatomical measurements might be useful to distinguish highly productive rubber tree clones.

METABOLISMO DO NITROGÊNIO ASSOCIADO À DEFICIÊNCIA HÍDRICA E SUA RECUPERAÇÃO EM GENÓTIPOS DE MILHO

Water stress affects deeply plant cell metabolism. The objective of this work was to quantify the effects of water deficits and its recovery on the performances of nitrogen metabolism enzymes: nitrate reductase (NR), glutamine sintethase (GS) and glutamate sintase (GOGAT) and an accumulation of proline in maize genotypes BR 2121 and BR 205. The trial was carried out in greenhouse, by using pots with 14.3kg of soil. The treatments performed were a combination of two genotypes and four intervals among irrigation (1, 3, 5 and 7 days). On the day in which the treatments were evaluated (49 days after emergency), there was irrigation on the treatments with intervals of 3 and 7 days, therefore those treatments were considered as light and severe recovery of water deficit, respectively. The extractions and analysis were performed by taking the third leaf completely expanded from top to down. The activities of enzymes did not differ among water deficit treatments, control and recovery of severe stress showed higher enzymatic activity than control. The accumulation of free proline in the leaves increased with deficit and responded to recovery of water deficit by reducing its content. In general, the enzimatic activity and the proline accumulation showed inverse answers within treatments.

Photosynthetic behaviour during the leaf ontogeny of rubber tree clones (Hevea brasiliensis (Wild. ex. Adr. de Juss.) Muell. Arg.), in Lavras, MG

Este trabalho, propos-se a investigar mudancas no comportamento fotossintetico durante a ontogenia foliar dos clones de seringueira PB 235, RRIM 600 e GT 1, em Lavras, MG. O experimento foi realizado no periodo de maio a julho de 2004, em condicoes de campo, na Universidade Federal de Lavras. Durante a ontogenia foliar avaliaram-se as seguintes caracteristicas: os teores de clorofilas, as trocas gasosas e a fluorescencia da clorofila. Os clones apresentaram perfis semelhantes de alteracoes nas caracteristicas fisiologicas avaliadas durante o desenvolvimento foliar. Ate o 32o dia de idade foliar (estadio B2), a fotossintese liquida foi negativa, devido a ineficiencia do sistema fotossintetico, sendo esta justificada pelos seguintes fatores: reduzidos teores de clorofilas, menor condutância estomatica, alta concentracao interna de CO2 e baixa fluorescencia de clorofilas. A partir do 37o dia de idade foliar, a fotossintese liquida tornou-se positiva e gradativamente maior, estimulada por aumentos nos teores de clorofilas, eficiencia fotoquimica do fotossistema II, eficiencia de carboxilacao, condutância estomatica, transpiracao e eficiencia no uso da agua. Entre os clones, o comportamento fotossintetico foi semelhante, atingindo desempenho maximo no 57o dia de idade foliar (estadio D), quando o clone RRIM 600 apresentou a maior taxa de fotossintese liquida diferenciando-se significativamente dos clones PB 235 e GT 1.

Alterações morfofisiológicas em folhas de cafeeiro (Coffea arabica L.) consorciado com seringueira (Hevea brasiliensis Muell. Arg.)

One alternative to reduce the effects of the production instability and of the insecurity of world budget over coffee growers is the cultivation of rubber tree intercropped with coffee. However, the productivity of both cultures is affected strongly by the climatic variations and for the crop system. The objective of this research was to perform evaluations of gas exchanges, chlorophyll fluorescence (Fv/Fm ratio) and leaf anatomy of coffee trees in cropped in different systems with rubber tree and environment. Four intercropping systems were studied as described: full sun coffee (C), three coffee cultivation lines between double strip of rubber tree (SSCCCSS), one coffee cultivation line between rubber tree strips (SCS) and three coffee plants for one rubber tree in the same cultivation line (SCSCS). The coffee plants of the (SSCCCSS), (SCS) and (SCSCS) systems showed smaller values of net photosynthesis rate (A), stomatal conductance (gs) and transpiration (E) and highest values of Fv/Fm ratio than that observed for the (C) system. The coffee plants cropped in the (C) system presented the highest average leaf thickness and also the largest thickness of palisade and lacunar parenchymas and stomatal index. These results indicate that coffee leaves have a great anatomic plasticity when cropped at full sun light or under shaded caused by rubber trees.

Trocas gasosas de cafeeiros (Coffea arabica L.) e seringueiras (Hevea brasiliensis Muell. Arg.) em diferentes sistemas de cultivo na região de larvas, MG

Crop systems that improve conservation of natural resources and diversity of production is a promising practice for farmers seeking low costs and a sustainable agriculture. The coffee - rubber tree intercropping has been studied in the south of Minas Gerais - Brazil. Within this context, the objective of this work was to evaluate the characteristics gas exchange, chlorophyll fluorescence and water relations of coffee and rubber tree in both intercropping and monocroping systems, in the early stage of the plantation establishment. The results showed that the reduction in radiation levels and temperature promote gas exchange increase in coffee, while higher photosynthetic radiation values and soil water availability are favorable to rubber tree in intercropping systems.

Similaridade genética entre clones de seringueira (Hevea brasiliensis), por meio de marcadores RAPD

A seringueira [Hevea brasiliensis (Willd. ex. Adr. de Juss) Muell.-Arg.] e uma especie nativa da regiao amazonica e compreende a maior fonte produtora de borracha natural do mundo. Na busca de condicoes mais favoraveis ao cultivo, alem da busca pela auto-suficiencia na producao de borracha natural, o cultivo da seringueira migrou para outras regioes do pais. Objetivou-se, com o presente trabalho, estimar a similaridade genetica de genotipos de seringueira, provenientes de regioes distintas do pais, Lavras-MG (UFLA) e Campinas-SP (IAC), por meio de marcadores moleculares RAPD. A analise foi efetuada em 41 individuos, representados por 17 genotipos diferentes, com base em 19 primers, que geraram 121 fragmentos polimorficos. Os dados foram analisados utilizando o software NTSYS-pc - 2.1, por meio do coeficiente de Dice e pelo metodo das medias (UPGMA). A similaridade genetica entre o material analisado variou de 0,56 a 1,00. Na analise do dendrograma, foram observados 18 grupos. Os clones (RRIM600, GT1, PB235, PL PIM e FX2261), utilizados em diferentes repeticoes, foram identicos, quando comparados entre si, entretanto o mesmo nao foi observado para os clones identificados como RRIM 701. Os resultados obtidos sugerem que o material avaliado na UFLA e o mesmo implantado no IAC, exceto o RRIM 701, mostrando uma ampla variabilidade genetica, disponivel para estudos e propagacao da cultura.

Sazonalidade da produção e características do látex de clones de seringueira em Lavras, MG

In spite of being the cradle of the species of the genus Hevea, Brazil contributed, in 2001, with only 1.5% of the world production of 7.132 million tons and it consumed around 3.5% of a total of 7.03 million tons of the world demand. The most productive clones are the orientals RRIM 600, PB 235 and PR 255, with production around 1,500 kg of dry rubber/ha/year. The cultivation of those clones in different regions in Brazil shows adaptation to several climatic patterns. The aim of this work was to evaluate the productive behavior of clones of rubber tree, associated to seasonal climatic and physiologic factors in relation to the latex production in Lavras, State of Minas Gerais, Brazil. The research was conducted in the experimental area of Biology Department of Federal University of Lavras, sector of Plant Physiology, between June 2001 and July 2003. The plant water relations and nutritional factors were appropriate to the productive period. The productivity of clone RRIM 600 was higher than the others and presented positive correlation to the environmental factors during the experimental period. The nutritional factors of the latex and the obstruction index showed significant correlation to the production.

Metabolism of carbohydrates during the development of seeds of the brazilian rubber tree [Hevea brasiliensis (Willd. Ex Adr. de Juss) Muell.-Arg.]

This work aimed at the assessment of the metabolism of carbohydrate during the development of the seeds of Brazilian rubber trees. The enzymatic activity of the acid invertase, neutral invertase and sucrose synthase (SuSy) and the levels of total soluble sugars (TSS), reducing sugars (RS) and sucrose were evaluated separately in each part of the fruit and seed—pericarp, seed coat, embryo and endosperm—on different days after the pollination (DAP). Based on the results obtained in this study, it is possible to conclude that in the beginning of the development of the rubber tree seeds, until 95 DAP, the endosperm presents high concentration of RS and low concentration of sucrose. After this period, the endosperm of the seed initiates starch accumulation and the concentration of RS decreases followed by the increase in the concentration of sucrose, presenting, after 120 DAP, an inversion of concentration of these two sugars. In the embryo, the levels of TSS, RS and sucrose show significant increase with the progress of the seed development. In the endosperm, the transition of the division phase and cell expansion for the storage of reserve material seem to occur around 120 DAP and is to be controlled mainly by the enzymes acid invertase and SuSy, while in the embryo, such transition seems to occur around 135 DAP and is to be controlled mainly by the enzymes acid and neutral invertases.

Growth, biophysical parameters and anatomical aspects of young rubber tree plants inoculated with arbuscular mycorrhizal fungi Glomus clarum

Mycorrhizal fungi are beneficial when associated with plants because they favor growth and develop. Although infrequent, artificial inoculation of arbuscular mycorrhizal fungi (AMF) has become an alternative to reduce the use of fertilizers and pesticides in crops, as well as for the formation of seedlings, to obtain precocious and well fed rootstocks. The objective of the study was to evaluate the effect of inoculation of AMF Glomus clarum on growth and biophysical and anatomical characteristics of young rubber trees. The treatments consist of plants inoculated with the fungus Glomus clarum and fertilized with 50 ppm of phosphorus (mic+50P), non-inoculated plants fertilized with 50 ppm of phosphorus (s/mic+50P) and non-inoculated plants fertilized with 500 ppm of phosphorus (s/mic+500P). The mycorrhizal plants showed height and stem diameter, dry matter accumulation of the aerial part, stomatal density and leaf area similar to the plants s/mic+500P. Greater accumulation of dry matter in the roots, higher transpiration rate, less stomatal resistance and lower leaf temperature were reported for the mycorrhizal plants. The anatomical analyses of the roots showed alterations in the vascular tissue, with increase in the number of xylem poles in the mycorrhizal plant roots.