RESUMO

RESUMEN Las plantas responden a cambios bióticos y abióticos acorde a su plasticidad fenotípica. Estas variaciones pueden expresarse en características relacionadas a la morfología foliar, crecimiento y defoliación. Este estudio evalúa la influencia de la edad de las plantas y de hojas sobre las características foliares, y su relación con la defoliación en tres especies forrajeras, Tithonia diversifolia, Morus alba y Moringa oleifera. M. oleifera mostró hojas con mayores valores de grosor, peso seco, asimetría y área; M. alba hojas más duras y con mayor área foliar especifica. M. oleifera el área foliar, peso seco, grosor y dureza incrementaron en plantas de 30 días. En tanto, que en M. alba las hojas intermedias tuvieron mayor área; y, las plantas de 90 días mayores valores de SLA, grosor y dureza. El área foliar y peso seco fueron mayores a los 60 y 30 días, respectivamente. En T. diversifolia las hojas intermedias presentaron mayor peso seco y grosor, las plantas de 30 días mayor área foliar y peso seco; y, las de 90 días, mayor grosor. Se encontraron relaciones negativas en hojas jóvenes con el grosor, dureza y peso seco. La defoliación mostró asociaciones positivas con el SLA y la dureza; y, negativas con el grosor, peso seco, asimetría y área. Subrayamos la importancia de realizar estudios que contribuyan al entendimiento de interrelaciones entre la estructura de la hoja, su función y sus relaciones con la expresión de los rasgos morfológicos de resistencia y tolerancia en especies tropicales de importancia económica y ecológica.

ABSTRACT Plants respond to biotic and abiotic changes through their phenotypic plasticity. These variations can be expressed in traits related to leaf morphology, plant growth, and defoliation. We evaluated the influence of plant age and leaf age on leaf traits and its relation with defoliation in three forage plant species, Tithonia diversifolia, Morus alba, and Moringa oleifera. Interspecifically, M. oleifera showed thicker leaves, higher dry weight, leaf asymmetry, and leaf area; M. alba showed harder leaves and higher specific leaf area. Intraspecifically, in the M. oleifera leaf area, dry weight, thickness, and hardness of leaves increased only in 30 day-old-plant. While in M. alba intermediate leaves had higher leaf area; and, 90 day-old-plant had higher thickness and hardness. Leaf area and dry weight were higher in 60 and 30 day-old-plants, respectively. In T. diversifolia intermediate leaves showed higher dry weight and leaf thickness, 30 day-old-plant had higher leaf area and leaf dry weight; and, 90 day-old-plant had higher leaf thickness. In addition, we found negative relationships between young leaves with leaf thickness, leaf hardness, and leaf dry weight. Defoliation showed positive relationships with SLA and leaf hardness, and negative ones with leaf thickness, leaf dry weight, leaf asymmetry, and leaf area. We underline, the importance of carrying out research that contributes to the understanding of the interrelationships between leaf structure, its function, and its relationships of morphological traits of plant resistance and tolerance in tropical forage plant species of high economic and ecological importance.

RESUMO

Plant-insect interactions are a determining factor for sustainable crop production. Although plants can resist or tolerate herbivorous insects to varying degrees, even with the use of pesticides, insects can reduce plant net productivity by as much as 20%, so sustainable strategies for pest control with less dependence on chemicals are needed. Selecting plants with optimal resistance and photosynthetic traits can help minimize damage and maintain productivity. Here, 27 landrace accessions of lima beans, Phaseolus lunatus L., from the Yucatan Peninsula were evaluated in the field for morphological resistance traits, photosynthetic characteristics, insect damage and seed yield. Variation was found in physical leaf traits (number, area, and dry mass of leaves; trichome density, specific leaf thickness and hardness) and in physiological traits (photosynthetic rate, stomatal conductance, intercellular carbon, water-use efficiency, and transpiration). Five accessions (JMC1325, JMC1288, JMC1339, JMC1208 and JMC1264) had the lowest index for cumulative damage with the highest seed yield, although RDA analysis uncovered two accessions (JMC1339, JMC1288) with strong positive association of seed yield and the cumulative damage index with leaf production, specific leaf area (SLA) and total leaf area. Leaf traits, including SLA and total leaf area are important drivers for optimizing seed yield. This study identified 12 important morphological and physiological leaf traits for selecting landrace accessions of P. lunatus for high yields (regardless of damage level) to achieve sustainable, environmentally safe crop production.