Joel Irineu Fahl

ENXERTIA DE COFFEA ARABICA SOBRE PROGÊNIES DE C. CANEPHORA E DE C. CONGENSIS NO CRESCIMENTO, NUTRIÇÃO MINERAL E PRODUÇÃO

Grafts of Coffea arabica L. onto C. canephora Pierre have been routinely used in regions infested with nematodes, due to the resistance of C. canephora to these pathogens. In the present work, growth, mineral nutrition and yield of two C. arabica cultivars grafted on C. canephora and C. congensis were evaluated in fields free from nematodes, in three coffee growing regions of Sao Paulo State, Brazil. Catuai Vermelho IAC H 2077-2-5-81 and Mundo Novo IAC 515-20 (two cultivars of C. arabica) were grafted on nematode resistant lines Apoata IAC 2258 and IAC 2286 of C. canephora and on IAC Bangelan colection 5 of C. congensis. Plants not grafted were used as controls, and plants grafted onto their own roots were also evaluated. Grafted cultivars after five years grew better and had higher yield than the ungrafted ones, specially the Catuai cultivar. Seasonal growth (plant height) was faster during spring and summer, for all treatmentes. In general, grafting increased height throughout the year, mainly during fall and winter seasons. Leaves of grafted plants had higher potassium and lower manganese content than ungrafted ones. Levels of other nutrients were not consistently affected by grafting.

Aspects of nitrogen metabolism in coffee plants

Coffee plants are highly N-demanding plants. Despite the importance of N nutrition for the development, acclimation and yield of coffee plants, there are few reports concerning N metabolism in this species. In this review, our intention is to summarize the information available in the literature and to point out the influence of environmental conditions on N assimilation, as well as com-ment and discuss some apparently contradictory results and raise and enlighten queries about N assimilation in coffee plants.Key words: Coffea, irradiance level, nitrate reductase, nitrogen fertilization, oxidative stress, photoinhbition, photoprotection, photosynthesis.Aspectos do metabolismo de nitrogenio em plantas de cafe: Plantas de cafedemandam grandes quantidades de N. Apesar da importância da nutricao nitrogenada para o desenvolvimento, aclimatacao e produtividade de plantas de cafe, sao poucos os trabalhos sobre o metabolismo de N nesta especie. A intensao desta revisao e sumarizar a informacao disponivel na literatura e discutir a influencia das condicoes ambientais na assimilacao de N, assim como comentar e discutir alguns resultados aparen-temente contraditorios e levantar e destacar perguntas sobre a assimilacao de N em plantas de cafe.Palavras-chave: Coffea, estresse oxidativo, fertilizacao nitrogenada, fotoinibicao, fotoprotecao, fotossintese, nivel de irradiância, redutase do nitrato.

Relações radiométricas de uma cultura de cana-de-açucar

Durante o periodo de maximo indice de area foliar de uma cultura de cana-de-acucar, cv. NA56-79, os coeficientes de reflexao, transmissao e absorcao da radiacao solar incidente variaram em funcao do ângulo de incidencia dos raios solares e da faixa espectral considerada. A radiacao fotossinteticamente ativa (PAR) foi sempre menos refletida e transmitida e mais absorvida que a radiacao do infravermelho proximo (NIR). Em geral, para as fracoes consideradas, obtiveram-se as seguintes relacoes radiometricas: (1) radiacao disponivel, NPAR = 1,2 NNIR; (2) radiacao refletida, RPAR = 0,1 RNIR; (3) radiacao transmitida, TPAR = 0,2 TNIR; (4) radiacao absorvida, APAR = 1,6 ANIR.

Distribuição da assimilação de nitrato e de matéria seca em plantas jovens de café cultivadas em diferentes níveis de nitrogênio

Nitrate assimilation and plant growth were examined In young coffee plants cultivated in sand in the greenhouse. The plants were supplied with nutrient solutions containlng 3.75, 7.5 and 15mM of nitrate. The distribution among the roots and shoots was assessed. Leaf area and leaf dry weight increased with nitrate concentration, while root dry weight and leaf pair number remained constant The in vivo nitrate reductase activity, assayed with and without exogenous nitrate in root tips was higher than In recently expanded leaves, and increased with nitrate concentration. The highest nitrate reductase activity, assayed with exogenous nitrate, revealed limitation to nitrate assimilation by substrate availability in both leaves and roots. Shoot growth was higher than root growth as afunctlon of increasing nitrogen levels.

Nitrate reduction in young coffee trees grown under different levels of light and nitrogen

The effect of levels of light and nitrogen on the activity of the enzyme nitrate reductase and its relationship with the availability of sugars and nitrate was studied in leaves of coffee plants (Coffea arabica L. cv. Catual). Ten month old plants were grown on pots containing a mixture of soil and compost, and were kept at full or 50% sunlight. Half of the plants of each light treatment received nitrogen supply. The results showed that the activity of nitrate reductase was higher on plants supplied with nitrogen at both light treatments. For the same nitrogen level, plants grown under full sunlight presented lower nitrate reductase activity, higher nitrate and sugars concentrations, and higher transpiration rates than plants kept at 50% sunlight. These results indicate that the lower nitrate reductase activity of plants grown under full sunlight was apparently not due to limitations of available nitrate and sugars to supply the energy necessary for nitrate reduction.

Partitioning of nitrate reductase activity in Coffea arabica L. and its relation to carbon assimilation under different irradiance regimes

The distribution of in vivo nitrate reductase (EC 1.6.6.1) activity (NRA) between leaves and roots was studied in young coffee plants (Coffea arabica L.) grown in pots with watered sand in a glasshouse and irrigated with nutrient solution. The influence of irradiance regimes on the partitioning of NRA, and its relation with CO2 assimilation, was also evaluated in plants grown under approximately 20, 50 and 100% of full sunlight. Time-course of nitrate accumulation in nitrogen-starved plants showed a similar pattern in leaves and roots after supplying 15 mmol L-1 nitrate, indicating efficient ability of the roots to export nitrate to the shoot. At the same time, NRA was rapidly induced in both tissues. In shoots, NRA partitioning was synchronized among the various leaf pairs. The initial increase in NRA, as each leaf pair emerged, coincided with the optimum NRA values of the next older leaf pair. However, the average shoot NRA remained relatively constant for each sampling date. During the first 23 weeks of vegetative growth, the mean NRA was 32% higher in leaves than in roots. The irradiance regimes influenced the partitioning of NRA between leaves and roots. The NRA leaf /root ratio was 0.72, 1.21 and 1.05, respectively, for plants grown under 20%, 50% and 100% of full sunlight. Leaf NRA was positively correlated with CO2 assimilation, in response to irradiance regimes. Under favorable CO2 assimilation conditions, higher NRA was observed in leaves than in roots, and the contrary trend occurred under limiting CO2 assimilation conditions. Under moderate irradiance regime the leaves were the main site of nitrate reduction, contributing with 70% of the whole plant nitrate assimilation.

EFEITO DA XYLELLA FASTIDIOSA EM CAFEEIROS EM DIFERENTES REGIÕES EDAFOCLIMÁTICAS (1)

A bacteria Xylella fastidiosa vem causando problemas para a cafeicultura, uma vez que sua presenca, associada a diversos fatores de estresse, provoca um decrescimo na producao devido a diminuicao no numero e tamanho dos frutos e a morte de alguns ramos. Este trabalho objetiva avaliar o efeito da X. fastidiosa sobre cultivares de Coffea arabica (enxertados ou nao) atraves da quantificacao da proporcao de vasos do xilema obstruidos pela bacteria, nas diferentes partes da planta e entre ramos com e sem sintoma da doenca, em experimentos desenvolvidos em diferentes regioes edafoclimaticas. Avaliou-se tambem a distribuicao das classes de infeccao nas diferentes partes da planta nos materiais geneticos estudados. Os experimentos foram instalados em 1986 em Mococa e Garca (SP) e as amostras para o estudo anatomico, retiradas em abril de 1998 e 2000 (periodo de estresse hidrico), respectivamente, das plantas de cafeeiros dessas areas. Na regiao de Mococa, observou-se que a nervura principal e o peciolo foram os tecidos com proporcao maior de vasos do xilema obstruidos pela X. fastidiosa; na regiao de Garca, foram o peciolo e o caule. Nao houve diferencas significativas na obstrucao de elementos de vaso do xilema do cafeeiro ocasionado pela bacteria entre as duas regioes estudadas. Nao houve tolerância a bacteria nos materiais geneticos, havendo no entanto variacao dentro de cada um deles. Na regiao de Garca, nas plantas de cafe, observou-se alta proporcao de vasos obstruidos nas raizes (3%), entretanto, nao houve dano maior na parte aerea.

Chilling Effects on Photosynthetic Activity and Membrane Leakage of Two Species of Coffea

Some plants of tropical and sub-tropical origin, such as coffee, suffer damage in the leaves or in the whole plant when submitted to low positive temperatures. The more frequent and the longer the periods of low temperatures, the more serious are the consequences for the plant. In sensitive species, the photosynthetic apparatus may be permanently impaired even with a short-term chilling (1).

Eficiência do nicosulfuron no controle de capim-massambara na cultura do milho

Um experimento de campo foi conduzido em Rio Claro, SP, em 1991/92 para estudar a eficiencia do nicosulfuron no controle do capimmass ambara (Sorghum halepense), como infestante da cultura do milho. O nicosulfuron foi aplicado em pos-emergencia inicial, quando o capim-massambara estava com 3 a 5 folhas, nas doses de 40, 50, 60, e 80g/ ha, e em pos-emergencia tardia (capim-massambara com 4 a 6 folhas), nas doses de 50, 60 e 80g/ha. Foram acrescentados tratamentos com atrazine + simazine (1500 + 1500g/ha), com e sem a adicao de oleo mineral, nas mesmas epocas de aplicacao do nicosulfuron. Verificou-se que o nicosulfuron apresentou excelente controle do capim massambara, atingindo 100% de controle aos 50 dias apos a aplicacao, independente das doses e epocas de aplicacao. As aplicacoes de atrazine + simazine nao mostraram controle satisfatorio do capim massambara em pos-emergencia, principalmente quando efetuadas tardias e com adicao de oleo mineral. O controle do capimmassambara com nicosulfuron em pos-emergencia inicial e tardia aumentou a producao de milho, respectivamente em 44 e 34%, em relacao a testemunha nao capinada. Nao foi observado qualquer sinal de fitotoxicidade nas plantas de milho, em todos os tratamentos efetuados.

Effects of growth regulators on the development and flowering of geranium plants

Com a finalidade de verificar a eficiencia de fitorreguladores no controle da altura de gerânio (Pelargonium hortorum Bailey) e no comprimento do raquis de sua inflorescencia, instalaram-se dois ensaios na regiao de Cotia, SP, ambos plantados em vasos em casa de vegetacao. Num deles, foram pulverizados clormequate e daminozide, nas doses de 1.000, 2.000 e 4.000 ppm por planta, e paclobutrazol nas doses de 15, 30 e 60 ppm. No segundo ensaio, foram pulverizados clormequate a 2.000ppm, por duas vezes e, em aplicacao unica, daminozide a 4.000 ppm e paclobutrazol nas doses de 5, 10 e 15 ppm. Clormequate e daminozide, de modo geral, nao foram eficientes na reducao do porte das plantas nem do comprimento do raquis da inflorescencia. Paclobutrazol, em todas as doses superiores a 5ppm, provocou reducao significativa tanto na altura das plantas como no comprimento do raquis da inflorescencia, destacando-se as concentracoes de 10 e 15 ppm como as mais adequadas para obtencao de plantas com conformacao ideal para envasamento.