Foliar Functional Traits of Resource Island-Forming Nurse Tree Species from a Semi-Arid Ecosystem of La Guajira, Colombia.

Semi-arid environments characterized by low rainfall are subject to soil desertification processes. These environments have heterogeneous landscapes with patches of vegetation known as resource islands that are generated by nurse species that delay the desertification process because they increase the availability of water and nutrients in the soil. The study aimed to characterize some foliar physiological, biochemical, and anatomical traits of three nurse tree species that form resource islands in the semi-arid environment of La Guajira, Colombia, i.e., Haematoxylum brasiletto, Pithecellobium dulce, and Pereskia guamacho. The results showed that H. brasiletto and P. dulce have sclerophyllous strategies, are thin (0.2 and 0.23 mm, respectively), and have a high leaf dry matter content (364.8 and 437.47 mg/g). Moreover, both species have a high photochemical performance, reaching Fv/Fm values of 0.84 and 0.82 and PIABS values of 5.84 and 4.42, respectively. These results agree with the OJIP curves and JIP parameters. Both species had a compact leaf with a similar dorsiventral mesophyll. On the other hand, P. guamacho has a typical succulent, equifacial leaf with a 97.78% relative water content and 0.81 mm thickness. This species had the lowest Fv/Fm (0.73) and PIABS (1.16) values and OJIP curve but had the highest energy dissipation value (DIo/RC).

Conformationally Restricted Peptides from Rice Proteins Elicit Antibodies That Recognize the Corresponding Native Protein in ELISA Assays.

The rice hoja blanca virus (RHBV), transmitted by the planthopper insect Tagosodes orizicolus, is a disease that attacks rice and generates significant production losses in Colombia. Fedearroz 2000 and Colombia I commercial rice varieties, which have different resistance levels to the disease, were selected in this study. To identify proteins associated to the insect and virus signaling, a comparative proteomics study was performed. By comparing proteomic profiles, between virus-infected and control group plants in two-dimensional electrophoresis, proteins exhibiting significant changes in abundance were found. In another test, peptide dendrimers containing sequences conformationally restricted to α-helix from four of those rice proteins were synthesized. In the experiment, sera from mice inoculated with peptide dendrimers could recognize the corresponding native protein in ELISA assays. Reported comparative proteomic results provide new insights into the molecular mechanisms of plant response to the RHBV and comprehensive tools for the analysis of new crop varieties. Besides, results from conformational peptide dendrimer approach are promising and show that it is feasible to detect proteins as markers, and may have biological applications by decreasing the susceptibility to proteolytic degradation.

ESTUDIO COMPARATIVO DE LOS COMPUESTOS VOLÁTILES DE TRES VARIEDADES DE GUAYABA BLANCA (Psidium guajava L.) DURANTE SU MADURACIÓN / COMPARATIVE STUDY OF VOLATILE COMPOUNDS OF THREE WHITE GUAVA VARIETIES (Psidium guajava L.) DURING RIPENING / ESTUDO COMPARATIVO DE COMPOSTOS VOLÁTEIS DE TRÊS VARIEDADES DE GOIABA BRANCA (Psidium guajava L.) DURANTE A MATURAÇÃO

La formación de los compuestos volátiles durante la maduración de la guayaba (Psidium guajava L.) ha sido un aspecto ampliamente estudiado; sin embargo, se desconocen los cambios de estos compuestos en variedades blancas de los cultivos colombianos como Guavatá Victoria (GV), Regional Blanca (RB) y Ráquira (RQ). Se utilizó el método Headspace-Microextracción en Fase Sólida (HS-MEFS) para comparar los perfiles olfativos de tres variedades de guayaba blanca de la región de la hoya del río Suárez (Santander, Colombia) durante tres etapas de maduración (verde, pintón y maduro). En las tres variedades se presentó un comportamiento similar, los aldehidos C-6 (hexanal, (Z)-3-hexenal y (E)-2-hexenal) responsables de la nota verde disminuyen durante la maduración, mientras que el contenido de ésteres (acetato de hexilo y acetato de (Z)-3-hexenilo) aumenta produciéndose las notas dulce y frutal características de la fruta madura. Los compuestos ácidos, furánicos y alcoholes se observan en bajas proporciones durante las tres etapas. El análisis de los compuestos volátiles mediante HS-MEFS permitió establecer una relación entre la transformación de compuestos aldehídos C6, responsables de la nota verde, en ésteres análogos, a los cuales se les atribuye la nota frutal característica durante el proceso de maduración.

The composition of volatile compounds during guava ripening (Psidium guajava L.) has been an aspect broadly studied. However, the changes of these compounds in representative white varieties from Colombia, like Guavatá Victoria (GV), Regional Blanca (RB) and Ráquira (RQ) are still unknown. Comparison of the aroma profiles was done using heads-pace-Solid Phase Micro Extraction (HS-SPME) for three white guava varieties from the Suárez River Basin region (Santander, Colombia) during three maturation stages (green, half-ripened and ripen). The three varieties presented a similar behavior, the C6- aldehydes (hexanal, (Z)-3-hexenal and (E)-2-hexenal) characterized for a green note diminished during ripening, while ester amounts (hexyl acetate and (Z)-3-hexenyl acetate) increase, producing sweet and fruity notes characteristics in a ripen fruit. The acids, furanics and alcohol compounds are present in low proportions at the three stages. Through HS-SPME analysis, we established a relation between C6-aldehy-des compounds transformation, responsible of the green note, into analogue esters that contribute to the fruity note during the ripening process.

A formação dos compostos voláteis durante o processo de amadurecimento da goiaba (Psidium guajava L.) tem sido muito estudada. Entretanto, pouco se conhece sobre as mudanças desses compostos nas variedades brancas representadas pela Guavatá Victoria (GV), Regional Blanca (RB) e Ráquira (RQ) na região do rio Suárez (Santander-Colômbia). O emprego da técnica HS-MEFS (Heads-pace-Microextração em fase sólida) para comparar o perfil olfativo durante as etapas da maturação (verde, semimaduro e maduro) mostrou um comportamento similar nas três variedades de goiaba branca: os aldeídos C-6 (hexanal, (Z)-3-hexe-nal e (E)-2-hexenal), caracterizados por uma nota verde, diminuíram ao longo do amadurecimento, enquanto que o conteúdo de ésteres (acetato de hexilo e acetato de (Z)-3-hexenilo) aumentou, produzindo as notas doces e frutal caracteristicas da fruta madura. Os compostos ácidos, furânicos e alcoólicos foram observados em baixas concentrações nas três etapas de maturação. Por fim, a técnica HS-MEFS permitiu detectar a rápida transformação dos compostos aldeídos C6, causadores da nota verde em ésteres análogos que causam a nota frutal durante o processo da maturação.