Nei Fernandes Lopes

Assimilate partitioning and phytotoxicity in soybean plants treated with herbicides

O efeito dos herbicidas trifluralin, clorimuron e clomazone sobre a morfologia e particao de assimilados foram avaliados durante o desenvolvimento da soja, cultivada em casa de vegetacao. As amostras foram coletadas a intervalos de 14 dias. Clamazone reduziu o acumulo de materia seca nos caules e folhas aos 14 dias apos a emergencia (DAE), enquanto que trifluralin e clorimuron reduziram o acumulo de materia seca ate os 28 DAE. O numero de folhas, a altura de planta, a massa e o numero de vagens e sementes, bem como a relacao parte aerea/raiz nao foram influenciadas pelos herbicidas. As raizes, os caules e as folhas foram os drenos preferidos ate o estadio R2 posteriormente, as vagens e sementes em desenvolvimento tornaram-se os drenos preferidos, esta sequencia nao foi alterada pelos herbicidas.

Sítios de penetração do quinclorac em sementes e plântulas de pepino e capim-arroz

The experiments were carried out under greenhouse or laboratory conditions at Vicosa, State of Minas Gerais, Brazil, in order to determine the preferential sites of quinclorac uptake in seeds and seedlings of Echinochloa spp. and Cucumis sativus L. cv. Caipira AG 221. The quinclorac was efficiently uptaken by seed, radicle, coleoptile or hypocotyl of barnyardgrass and cucumber. The herbicide uptake by radicle produced great reduction on elongation and dry weight of shoots and roots in both species, indicating that radicle may be the preferencial site of quinclorac penetration in young structures. The quinclorac induced visual symptoms of phytotoxicity or morphological alterations in cucumber and barnyardgrass plants.

Efeito do 2,4-D e do glifosate no controle da parte aérea e dos rizomas da losna

It is difficult to obtain an efficient mechanical and chemical control of wormwood (Artemisia verlotorum) because this weed has a great capacity to sprout and is tolerant to most herbicides. The rate of 1,662 kg/ha of 2,4-D reduced the number of living plants from 34 to 6 after 30 days application. However, glyphosate (0,856 kg/ha) reduced the number of living plants from 27 to 10 in field conditions. After 60 days application, the number of living plants was reduced from 34 to 18 by 0,811 kg/ha of glyphosate. However, no differences were found for application rates of 2,4-D at the same conditions. None of treatments showed satisfactory performance in relation to wormwood after 90 days application in field conditions. In greenhouse, glyphosate treatments reduced rhizome sprout, though, no differences were found for application rates of 2,4-D. The rates of 1,0 and 0,865 kg/ha of glyphosate resulted in lower dry matter weigth of aerial part of the wormwood and its rhizomes, respectively. Leaf area was reduced with glyphosate (0,983 kg/ha) at the same conditions.

Controle químico da losna em plantio direto de trigo

It is difficult to obtain an efficient mechanical and chemical control of wormwood (Artemisia verlotorum) because this weed has a great capacity to sprout and is tolerant to most herbicides. Natural areas infested with wormwood were treated with glyphosate and 2,4-D. Glyphosate was more efficient than 2,4-D on wormwood control. The application of 2,4-D did not cause significant differences on wormwood control 90 days after treatment. However, the glyphosate had prolonged effect, decreasing the number of living plants until 90 days after its application. Intermediary rates were more effecient than higher rates on wormwood control. Higher values of all studied characteristics of wheat crop were obtained with intermediary rates of both herbicides. Higher yield of wheat (3787 kg/ha) were obtained when 0,721 kg/ha of glyphosate associated with 1,152 kg/ha of 2,4-D was applied.

Efeito do quinclorac sobre algumas características morfológicas do arroz irrigado

This assay was carried out under greenhouse conditions at Vicosa, State of Minas Gerais, Brazil. The effects of quinclorac rates on morphological characteristics of irrigated rice (Oryza sativa L. cv. Inca) were evaluated at 7, 14 and 21 days after treatment. The cultivar Inca showed high tolerance to the herbicide. Leaf area and dry weight leaf at 21 days after treatment were inhibited by 50% only at rates 5 and 7 fold of the common doses used, respectively. Plant height was not decreased by quinclorac until the last harvest. No visual symptoms of phytotoxicity caused by quinclorac was detected.

Desenvolvimento, partição de assimilados e produção de matéria seca de plantas de soja (Glycine max (L.) merrill) submetidas a quatro doses de metribuzin

Development, assimlate partition and dry matter production in soybean (Glycine Max (L.) Merri ll, cv. Uberaba) plants treat ed with four metri buzin doses (0,0; 0,35; 0,70 and 1,05 kg i.a.ha-1) were studied in a field experiment. Metribuzin did not reduce the stand or alter ed significantly shoot /root ratio. Plants height average incre ased as the doses of metribuzin increased; maximum heights were 761, 784, 815 and 812 mm, for increasing metribuzin doses. Metribuzin did not alter the pattern of sequential dry matter partition in the plants. Metribuzin did not affect dry matter accumulation in pods (Wv); however, from initiation to the end of maturation of seeds the control presented greater Wv values than trea plants, due to its highest net assimilation rate after blooming. Pericarp dry matter (Wp) was decre ased from full development se eds to final harvest for all treatments, except for Wp of plant streated with 0,7 i.a.ha-l that was maintained practically. Constant on the other hand, seed dry matter increased accentuately, from formation to last harvest, for all doses employed.