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The benzothiadiazole compound acibenzolar-S -methyl (ASM) was assessed as an inducer of resistance against Crinipellis perniciosa , agent of witches' broom, and Verticillium dahliae , agent of vascular wilt, both on cocoa. ASM induced a reduction in incidence of witches' broom of up to 84·5% when sprayed 30 days before inoculation on cocoa seedlings of cv. Catongo. ASM also induced a reduction in severity of Verticillium wilt to 55·4% on cv. Theobahia. For both pathosystems, effects of dose on disease were not clearly observed. The efficacy of the inducer increased with the interval between sprayings and the respective inoculations with the pathogens. In another experiment, the effect of ASM on the control of witches' broom on cocoa seedlings was compared with that of cuprous oxide and tebuconazole, all sprayed 15 days before inoculation. ASM reduced disease incidence by 60·1% compared with the inoculated control. ASM was superior to tebuconazole, and there was also a tendency for ASM to be better than cuprous oxide. To understand the mechanism of action of ASM as an inducer of resistance, alterations in the levels of total phenolics, polyphenol oxidases and peroxidases were evaluated 3, 15 and 30 days after spraying of seedlings of cv. Catongo. Enzyme activities from seedlings of cv. Theobahia were evaluated 30 days after spraying. On cv. Catongo, no significant differences in total phenolic content and polyphenol oxidase activity were detected after spraying. However, an increase in peroxidase activity was detected at all times of evaluation. On cv. Theobahia, significant increases in activities of peroxidase and polyphenol oxidase were detected, indicating that defence responses due to ASM were dependent on host genotype.

-The objective of this work was to evaluate the physiological and anatomical traits of plants of a cacao (Theobroma cacao) clone in response to water deficit after leaf application of silicon. A randomized complete block design was used, with four replicates, in a 2x3 factorial arrangement of two water regimes (irrigated or nonirrigated) and three silicon concentrations (0.0, 1.5, and 3.0 mg mL -1 ) applied in wettable SiO 2 powder. The plants were evaluated 20 days after the irrigation regimes were applied. The use of SiO 2 increased the stability of cell membranes and the photochemical efficiency of the plants under water deficit. The 1.5 mg mL -1 concentration of SiO 2 increased photosynthetic rate, water use efficiency, and carboxylation efficiency, besides mitigating the effect of oxidative stress. Stomatal density was reduced in nonirrigated plants under the highest concentration of Si. The 1.5 mg mL -1 concentration of Si is considered optimal for the photosynthetic metabolism of young cacao plants under soil water limitation.Index terms: Theobroma cacao, anatomy, antioxidant enzymes, drought, photochemistry, SiO 2 . Aplicação foliar de silício em plantas jovens de cacau submetidas à deficiência hídricaResumo -O objetivo deste trabalho foi avaliar as características fisiológicas e anatômicas de plantas de um clone de cacau (Theobroma cacao) em resposta ao deficit hídrico após a aplicação foliar de silício. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições, em arranjo fatorial 2x3, com dois regimes hídricos (irrigado e não irrigado) e três concentrações de silício (0, 1,5 e 3,0 mg mL -1 ) aplicadas como pó molhável de SiO 2 . As plantas foram avaliadas 20 dias após a aplicação dos regimes de irrigação. O uso de SiO 2 aumentou a estabilidade das membranas celulares e a eficiência fotoquímica das plantas sob deficit hídrico. A concentração de 1,5 mg mL -1 de SiO 2 aumentou a taxa fotossintética, a eficiência do uso da água e a taxa de carboxilação, além de ter mitigado o efeito do estresse oxidativo. A densidade estomática foi reduzida em plantas não irrigadas sob a maior concentração de Si. A concentração de 1,5 mg mL -1 de Si é considerada ótima para o metabolismo fotossintético de plantas jovens de cacau sob limitação de água no solo.Termos para indexação: Theobroma cacao, anatomia, enzimas antioxidantes, seca, fotoquímica, SiO 2 .

Resumo -Genótipos de Theobroma cacao L. devem ser melhor estudados, para se identificar aqueles que produzem sementes mais desenvolvidas e viáveis após o armazenamento. Objetivou-se com este trabalho estudar a biometria e dois tempos de armazenamento de sementes de genótipos de cacaueiro. A biometria foi avaliada em oito genótipos de cacaueiro (tratamentos). Foram instalados testes de germinação em delineamento inteiramente ao acaso, no esquema fatorial 8 x 2 (genótipos: CCN51, PH16, CEPEC2002, Ipiranga, SJ02, PS1319, TSH1188 e Comum x dois períodos de armazenamento: 0 e dois dias). O genótipo TSH1188 apresentou maior comprimento, relação comprimento/largura, espessura e massa de 100 sementes. A absorção de água das sementes recém-colhidas dos genótipos é lenta, justificada pelos altos teores de água, o que não caracteriza padrão-trifásico. Os teores de água reduziram em média 2,3 vezes nas sementes armazenadas em relação às recém-colhidas. A germinação das sementes recém-colhidas dos genótipos foi de 100%. Após o armazenamento, as sementes do PS1319 apresentaram a menor redução da germinação (39%), enquanto as dos PH16, CEPEC2002 e SJ02 reduziram 96%. A velocidade de germinação foi maior e o tempo médio menor que dois dias nas sementes recém-colhidas do PS1319, indicando serem mais tolerante à dessecação. Sugere-se o uso dos genótipos TSH1188 e PS1319 em programas de melhoramento genético. Biometrics and storage of cocoa seeds genotypesAbstract -Genotypes of Theobroma cacao L. should be further studied to identify those that produce more developed and viable seeds after storage. The objective of this work was to study biometrics of cacao seeds genotypes and two periods of seed storage. Seeds biometrics were evaluate in eight cacao genotypes (treatments). Germination tests were carried out in completely randomized design in a factorial 8 x 2 (genotypes: CCN51, PH16, CEPEC2002 Ipiranga, SJ02, PS1319, TSH1188 and Comum x two periods of storage: 0 and two days). TSH1188 showed higher length, length/width, thickness and weight of 100 seeds. Water absorption of freshly harvested seed of the genotypes is slow, justified by the high water content, which does not characterizes standard features. Water levels were reduced on average 2.3 times in stored seeds compared to freshly picked. Germination of freshly harvested seeds of any genotype was 100%. However, after storage, PS1319 seeds showed the least reduction in germination (39%), whereas PH16, CEPEC2002 and SJ02 reduced 96%. Germination rate was higher, and average time less than two days in freshly harvested seeds of PS1319, indicating tolerance to desiccation. It is suggested the inclusion of genotypes TSH 1188 and PS1319 in breeding programs seeds.

This study aimed to characterize the alarm and resistance phases of stress of Caesalpinia echinata under intense irradiance in order to better define its position on forest succession. The alarm phase was identified by rapid reduction in the maximum quantum yield of PSII primary photochemical reactions (φP0 = F V /F M ) and Performance Index (PI ABS ) followed by total leaf abscission in the first week of exposure to direct sunlight. The new leaves grown showed recovery of chlorophyll a parameters, increase in blade thickness, elongation of the palisade and spongy parenchymas, higher water content, and reduction of specific leaf area. These changes were associated with the osmoprotector of sucrose and antioxidative of raffinose effects, which indicate an efficient adjustment system to intense irradiance in the resistance phase of stress. However, the continuous decrease in photosynthetic pigments in the resistance phase combined with the photodamage in the fluorescence of Chl a and total abscission of leaves in the alarm phase are strong indications that C. echinata is a shade and late or climax species in forest succession.