Increased synthesis of galactinol and raffinose family oligosaccharides (RFOs) has been reported in vegetative tissues in response to a range of abiotic stresses. In this work, we evaluated the transcriptional profile of a Coffea canephora galactinol synthase gene (CcGolS1) in two clones that differed in tolerance to water deficit in order to assess the contribution of this gene to drought tolerance. The expression of CcGolS1 in leaves was differentially regulated by water deficit, depending on the intensity of stress and the genotype. In clone 109A (drought-susceptible), the abundance of CcGolS1 transcripts decreased upon exposure to drought, reaching minimum values during recovery from severe water deficit and stress. In contrast, CcGolS1 gene expression in clone 14 (drought-tolerant) was stimulated by water deficit. Changes in galactinol and RFO content did not correlate with variation in the steady-state transcript level. However, the magnitude of increase in RFO accumulation was higher in the tolerant cultivar, mainly under severe water deficit. The finding that the drought-tolerant coffee clone showed enhanced accumulation of CcGolS1 transcripts and RFOs under water deficit suggests the possibility of using this gene to improve drought tolerance in this important crop.

Polyploid plants can exhibit transcriptional modulation in homeologous genes in response to abiotic stresses. Coffea arabica, an allotetraploid, accounts for 75% of the world's coffee production. Extreme temperatures, salinity and drought limit crop productivity, which includes coffee plants. Mannitol is known to be involved in abiotic stress tolerance in higher plants. This study aimed to investigate the transcriptional responses of genes involved in mannitol biosynthesis and catabolism in C. arabica leaves under water deficit, salt stress and high temperature. Mannitol concentration was significantly increased in leaves of plants under drought and salinity, but reduced by heat stress. Fructose content followed the level of mannitol only in heat-stressed plants, suggesting the partitioning of the former into other metabolites during drought and salt stress conditions. Transcripts of the key enzymes involved in mannitol biosynthesis, CaM6PR, CaPMI and CaMTD, were modulated in distinct ways depending on the abiotic stress. Our data suggest that changes in mannitol accumulation during drought and salt stress in leaves of C. arabica are due, at least in part, to the increased expression of the key genes involved in mannitol biosynthesis. In addition, the homeologs of the Coffea canephora subgenome did not present the same pattern of overall transcriptional response, indicating differential regulation of these genes by the same stimulus. In this way, this study adds new information on the differential expression of C. arabica homeologous genes under adverse environmental conditions showing that abiotic stresses can influence the homeologous gene regulation pattern, in this case, mainly on those involved in mannitol pathway.

Pesq. agropec. bras., Brasília, v.40, n.9, p.943-946, set. 2005 Resumo -O efeito da embebição de sementes de algodão cultivar IPR-120 com cloreto de mepiquat no crescimento e desenvolvimento inicial das plantas foi avaliado em casa de vegetação. Os tratamentos foram arranjados em esquema fatorial 5x3 (cinco concentrações do produto, três tempos de embebição), com cinco repetições. Altura e área foliar foram avaliadas, da emergência até o início do florescimento. Os tratamentos com cloreto de mepiquat reduziram a altura da planta desde a emergência, com interações entre os fatores analisados. O número de botões florais e de ramos, a área foliar, a matéria seca da parte aérea e a altura da inserção do nó cotiledonar também foram reduzidos pelos tratamentos.Termos para indexação: Gossypium hirsutum, regulador de crescimento, altura de plantas, tratamento de sementes, inibidores de crescimento. Development of cotton plant from seeds soaked with mepiquat chlorideAbstract -The effects of cotton seeds cultivar IPR-120, soaked with mepiquat chloride solutions on the initial growth and development of the plants, grown in 2,5 L plastic bags, were evaluated under greenhouse conditions. Treatments comprised five mepiquat chloride concentration solutions and three soaking durations, with five replications. Evaluations were carried out weekly from emergence to beginning of flowering stage. The treatments containing mepiquat chloride soaking reduced plant height since the emergence, with some interactions among the factors. They also reduced the number of flower buds and branches, leaf area, dry matter and the height of the cotyledon node.

No abstract

RESUMOFoi avaliado o efeito do tratamento de sementes de algodão, cultivar IPR 120, embebidas em soluções com cloreto de mepiquat e a interação com a aplicação foliar seqüencial deste produto no crescimento, desenvolvimento e produção de algodão, em condições de campo, em Londrina, PR. O delineamento experimental foi o de blocos casualizados, em esquema fatorial 5 x 2, sendo um fator a embebição das sementes com as concentrações de cloreto de mepiquat [0; 0,5; 2,5; 5 e 7,5% (v/v)] e o outro a aplicação foliar (aplicação e não), com quatro repetições. As duas primeiras aplicações foliares ocorreram aos 17 e 32 dias após emergência e as demais a cada 10 dias de intervalo, totalizando sete aplicações. A embebição com regulador afetou a altura da planta, a altura da inserção do nó cotiledonar, não tendo atuação sobre a altura da inserção do primeiro ramo produtivo, número total de ramos, número de ramos frutíferos, número de maçãs por planta e no número de maçãs na primeira posição dos ramos frutíferos, variáveis estas afetadas com aplicação foliar.Termos para indexação: Regulador de crescimento, aplicação parcelada, tratamento de semente, Gossypium hirsutum. ABSTRACTThe effect of soaking cotton seeds, cultivar IPR 120, in mepiquat chloride solution and foliar application of such substance on plant height, development and yield of cotton plants were evaluated. The experiment was carried out under field conditions in Londrina, PR, Brazil. Treatments were displayed in a completely randomized design using a random factorial (5X2): five concentrations of mepiquat chloride (0; 0.5; 2.5; 5.0 and 7.5% (v/v)) for seed soaking and two (0 and 120 g i.a.ha -1 ) foliar application, replicated four times. The first two applications were done at 17 and 32 days after emergence, and the remaining five at 10-day intervals. Seed treatment with mepiquat chloride affected plant and cotyledon node heights, but showed no effect on the first productive branch insertion and the total number of branches, reproductive branches, bolls per plant and first position bolls. All these variables were affected by the foliar application.