Significance of Plant Canopy Maintenance in Crop Yield

The yield of any crop depends on the capacity of a plant canopy to intercept and efficiently use the sunlight, which is dependent on canopy architecture of a plant viz., leaf size, shape and angle, number of leaves and branches, and a crop geometry viz., row orientation, row spacing, plant geometry, plant density, etc. The amount and distribution of leaf area in a crop canopy determine the way, by which, the photosynthetic active radiation is intercepted and consequently it influences the canopy photosynthesis and yield. The balance between the source and sink significantly contributes towards the higher accumulation of photosybthates Cropping geometry of a plant/crop affects the radiation use efficiency, intercepted photosynthetic active radiation (IPAR) and thereby the biological and economical yield of a crop. Optimum plant population stand and its density and a planting pattern with adequate spatial arrangement are important cultural factors that increase radiation interception and yield production.

MicroRNAs as potential targets for improving rice yield via plant architecture modulation: Recent studies and future perspectives

Ensuring agricultural food security is a major concern for the future world, and being the second mostconsumed crop, rice yield needs an urgent upliftment. Grain yield is a pleiotropic trait that employs a plethoraof genes functioning in complex signalling cascades. The yield related genes are controlled by variousregulatory factors including the microRNAs (miRNAs), the small 20–22 nucleotide (nt) non-coding RNAs,which have emerged as the master ribo-regulators of eukaryotic genes. Plant miRNAs can bind to highlycomplementary sequences in the target messenger RNAs (mRNAs) and negatively regulate gene expression tocoordinate the various biological processes involved in plant development. In rice, an ideal plant architecture(IPA) has been regarded as the key to attain high yield and several miRNAs have been deciphered to playimportant roles in orchestrating vital regulatory procedures for achieving optimum plant morphological yieldrelated traits like less unproductive tillers, more panicle branches and heavier grains. In this review, we presentand discuss the various genetic engineering strategies undertaken to manipulate the miRNA-mRNA expressionlevels in order to achieve improved grain output by modulation of rice plant architecture and recent advancesmade in this regard

Variación arquitectónica y morfológica de Hintonia latiflora (Rubiaceae) en relación a la cosecha de corteza y factores ambientales / Architectural and morphological variation of Hintonia latiflora (Rubiaceae) in relation to bark harvest and environmental factors

ResumenHintonia latiflora es una especie ecológicamente rara y económicamente importante del bosque tropical caducifolio de la Cuenca del Balsas, México, cuya corteza se comercializa como medicinal. Las prácticas de descortezado han modificado la forma de las plantas, su arquitectura y morfometría. Se desconoce, si además, existe influencia de factores topogáficos y edáficos sobre estos atributos. Se propone que las condiciones ecológicas en las áreas de distribución y cosecha determinarán las características morfométricas y la variación de la arquitectura de los individuos. Para probar esta hipótesis, evaluamos la relación de factores topográficos y edáficos en diferentes características morfológicas de juveniles (n = 143) y adultos (n = 117) de ocho zonas de cosecha de H. latiflora. Las zonas de cosecha, con una superficie de 0.6 ha, fueron seleccionadas al azar con el apoyo de mapas participativos elaborados por los recolectores del área de estudio. Los datos fueron analizados mediante componentes principales (ACP), y correspondencia canónica (ACC). Los primeros tres CP explicaron el 92.1 % de la variación morfológica; la altura, diámetro basal y cobertura fueron las variables que explicaron las diferencias morfométricas entre juveniles y adultos en las ocho zonas de cosecha. La pendiente del terreno, orientación de la pendiente, profundidad del suelo y pedregosidad, fueron los factores ecológicos estadísticamente relacionados con las diferencias morfométricas. Una menor pendiente, poca pedregosidad, profundidad de suelo, orientación E-O en juveniles (azimut 90˚-270˚) y N-S en adultos (azimuth 0˚-180˚), fueron los factores asociados a mayor altura, número de ramas basales, diámetro basal y cobertura en H. latiflora. Las zonas con mayor intensidad de cosecha estuvieron integradas por árboles monopódicos y algunos individuos basítonos reiterados. Los adultos de estas zonas tuvieron mayor número de frutos. En estos sitios, las plantas de H. latiflora fueron más abundantes y productivas para corteza, pero la alta intensidad de cosecha influyó en la arquitectura vegetal, formando individuos arbustivos multirramificados que originalmente fueron mesótonos. Las áreas con menor intensidad de cosecha estuvieron caracterizadas por pendientes abruptas, suelos superficiales y pedregosos, dominadas por árboles basítonos de menor talla, delgados y escasos en el área. Estos sitios son los menos recomendados para cosecha, debido a que producen menos corteza por árbol, pero sirven para mantener a la especie en el lugar. Con base en estos resultados, podemos desarrollar programas de rehabilitación en áreas afectadas por la explotación comercial, establecer plantaciones forestales en sitios clave para asegurar el desarrollo de individuos con características deseables para cosecha de corteza y contribuir a la conservación in situ de H. latiflora en la Cuenca del Alto Balsas.

AbstractHintonia latiflora is a rare ecologically and economically important species from the Tropical Deciduous Forest of the Balsas Basin, Mexico, whose bark is traded as medicinal. Debarking practices have modified the shape of plants, their architecture and morphometry; but it is unknown if some topographic and edaphic factors may also influence in these attributes. Here we propose that the ecological conditions of this species distribution and harvesting areas, may determine the morphometric characteristics and the individuals variation in their architecture. To test this hypothesis we assessed the relationship of topographic and edaphic factors on the morphological characteristics of saplings (n = 143) and adults (n = 117), in eight harvesting areas of H. latiflora. The harvesting areas, with a surface of 0.6 ha, were selected randomly with the support of participatory mapping elaborated by gatherers of the study site. Data were analyzed using principal components (PCA) and canonical correspondence (CCA) analyses. The first three PC explained 92.1 % of the morphological variation; height, basal diameter, and coverage, explained morphometric differences in both, saplings and adults, in all eight harvesting zones. The terrain slope, slope orientation, soil depth and stoniness, were ecological factors statistically related with morphometric differences. A lower terrain slope, little stoniness, soil depth, slope orientation E-W in saplings (azimuth 90˚-270˚) and N-S in adults (azimuth 0˚-180˚) were the factors associated to height, number of basal branches, basal diameter and coverage of H. latiflora. Areas with higher harvesting intensity were composed by monopodic trees and some reiterated basitone individuals; the adults of these areas also had more fruits. At these sites, plants of H.latiflora were more abundant and produced more bark, but the high-intensity of harvesting, changes plant architecture, forming shrubby, multi-stemmed individuals, that originally were mesotone trees. Areas with lower harvesting intensity were characterized by steep slopes, shallow and rocky soils, and were dominated by basitone trees of smaller size, thin and scarce in the area. These sites are the least recommended for harvesting, because they produce less bark per tree, and serve to preserve the species at the site. Based on these results, we can develop restoration programs in areas affected by commercial harvesting, establish forestry plantations in key sites to ensure the establishment and development of individuals with desirable characteristics for bark harvesting and contribute to in situ conservation of H. latiflora in the Alto Balsas Basin. Rev. Biol. Trop. 65 (3): 900-916. Epub 2017 September 01.

Does plant architectural complexity increase with increasing habitat complexity? A test with a pioneer shrub in the Brazilian Cerrado / A complexidade arquitetural de plantas aumenta com a complexidade do habitat? Um teste com um arbusto pioneiro de Cerrado

Understanding variation in plant traits in heterogeneous habitats is important to predict responses to changing environments, but trait-environment associations are poorly known along ecological gradients. We tested the hypothesis that plant architectural complexity increases with habitat complexity along a soil fertility gradient in a Cerrado (Neotropical savanna) area in southeastern Brazil. Plant architecture and productivity (estimated as the total number of healthy infructescences) of Miconia albicans (SW.) Triana were examined in three types of vegetation which together form a natural gradient of increasing soil fertility, tree density and canopy cover: grasslands (campo sujo, CS), shrublands (cerrado sensu strico, CE) and woodlands (cerradão, CD). As expected, plants growing at the CS were shorter and had a lower branching pattern, whereas plants at the CD were the tallest. Unexpectedly, however, CD plants did not show higher architectural complexity compared to CE plants. Higher architectural similarity between CE and CD plants compared to similarity between CS and CE plants suggests reduced expression of functional architectural traits under shade. Plants growing at the CE produced more quaternary shoots, leading to a larger number of infructescences. This higher plant productivity in CE indicates that trait variation in ecological gradients is more complex than previously thought. Nematode-induced galls accounted for fruit destruction in 76.5% infructescences across physiognomies, but percentage of attack was poorly related to architectural variables. Our data suggest shade-induced limitation in M. albicans architecture, and point to complex phenotypic variation in heterogeneous habitats in Neotropical savannas.

O entendimento da variação dos atributos de plantas em ambientes heterogêneos é importante para prever respostas às mudanças climáticas; entretanto, a resposta de atributos das plantas às mudanças ambientais é pouco conhecida ao longo de gradientes ecológicos. Testou-se a hipótese de que a complexidade arquitetural de Miconia albicans (SW.) Triana aumenta com a complexidade ambiental, ao longo de um gradiente de fertilidade de solo em um Cerrado no sudeste brasileiro. A arquitetura e a produtividade (estimada por meio do número total de infrutescências sadias) foram examinadas em três tipos de vegetação, que formam um gradiente de fertilidade de solo, de densidade de árvores e de cobertura vegetal: campo sujo (CS), cerrado sensu stricto (CE) e cerradão (CD). Plantas crescendo no CS foram menores e apresentaram menor complexidade arquitetural, enquanto plantas no CD foram maiores. No entanto, de forma inesperada, plantas no CD não demonstraram maior complexidade arquitetural quando comparadas às plantas de CE, e a maior similaridade arquitetural entre plantas de CE e CD, quando comparadas com plantas de CE e CS, sugere que a expressão de atributos funcionais da arquitetura é limitada sob condições de sombra. Plantas de CE produziram mais ramos quaternários e maior número de infrutescências, sendo que a maior produtividade destas plantas indica que a variação de atributos em gradientes ecológicos é mais complexa do que se pensava anteriormente. Galhas de nematóides destruíram 76,5% das infrutescências nas vegetações, mas a porcentagem de ataque não esteve fortemente correlacionada com as variáveis arquiteturais. Os resultados do presente trabalho sugerem limitação na expressão da arquitetura da planta induzida pela sombra e apontam para uma complexa variação fenotípica na colonização de ambientes heterogêneos de savanas neotropicais.

Allometry of the babassu palm growing on a slash-and-burn agroecosystem of the eastern periphery of Amazonia / Allometria da palmeira babaçu em um agroecossistema de derruba-e-queima na periferia este da Amazônia

Babassu (Attalea speciosa C.Martius, Arecaceae) is a palm with extraordinary socioeconomic and ecologic importance in large areas of tropical Brazil, especially in frequently burned and degraded landscapes. Nevertheless, surprisingly little is known about this keystone species. This paper investigates the allometry of babassu, in order to improve understanding on palm architecture and to provide researchers with an efficient tool for aboveground biomass estimation of juvenile and adult palms. Juvenile leaf biomass can be accurately predicted with the easily measurable minimum diameter of rachis at 30 cm extension. Adult palm biomass can be estimated based on woody stem height, a variable fairly easily measurable on-field. Leaf biomass of adult palms was highly variable, averaged 31.7 percent of aboveground biomass and can be estimated only indirectly through the relationships between wood:leaf-ratio and total aboveground biomass. Carbon contents varied little in the babassu palm, without size- or growth-stage related differences, suggesting the general applicability of values (42.5 percent C for stems, 39.8 percent C for leaves). As a consequence of the limited secondary diameter growth inherent to palms, stem diameter of adult palms is unrelated to palm height and biomass. Stem tapering decreases with increasing palm height. This is partially compensated by increasing wood density in near cylindrical stems. Nevertheless, maximum babassu palm height of about 30 meters appears to be dictated by mechanical stability constraints. All allometric relationships of babassu described in this study are not affected by vegetation stand age, indicating the general applicability of these relationships.

A palmeira babaçu (Attalea speciosa C.Martius, Arecaceae) tem grande importância socioeconômica e ecológica em grande parte da área tropical brasileira, especialmente em áreas degradadas por queimadas freqüentes na Amazônia. No entanto, ainda pouco se sabe sobre as características ecológicas desta espécie-chave. Este estudo investiga a alometria do babaçu com o objetivo de estabelecer uma metodologia eficiente na estimativa da biomassa aérea de palmeiras juvenis e adultas e para um melhor entendimento da sua arquitetura. A biomassa de palmeiras juvenis pode ser estimada facilmente e com precisão com o diâmetro mínimo das ráquis das folhas a 30 cm de extensão. A biomassa de palmeiras adultas pode ser estimada com base na altura do tronco lenhoso, também relativamente de fácil medição em campo. A biomassa foliar das palmeiras adultas foi em media 31,7 por cento da biomassa aérea, porém houve uma alta variação e, portanto, somente pode ser estimada indiretamente através da relação entre a razão madeira:folha e biomassa aérea total. Os teores de carbono no babaçu apresentaram baixa variação, sem diferenças sistemáticas em relação ao tamanho ou estágio de crescimento, o que aponta à aplicabilidade geral dos valores 42.5 por cento C para troncos, 39.8 por cento C para folhas. Em conseqüência do limitado crescimento secundário do diâmetro inerente de palmeiras, não houve relação do diâmetro de tronco com a altura e a biomassa das palmeiras adultas. Observou-se que o afilamento do caule diminui com o aumento da altura das palmeiras, o que é parcialmente compensado pelo incremento da densidade de madeira em troncos quase-cilíndricos. No entanto, a altura máxima do babaçu, de cerca de 30 metros, aparentemente está definida por limitações na estabilidade mecânica. Todas as relações alométricas aqui descritas são independentes da idade da vegetação, indicando a aplicabilidade geral das relações encontradas.