Influence of low light intensity on growth and biomass allocation, leaf photosynthesis and canopy radiation interception and use in two forage species of Centrosema (DC.) Benth.

Abstract

Sustainable silvopastoral systems rely on the capacity of forage species to withstand shade, competition for soil resources and grazing. On a field‐plot experiment, we studied the effects of artificial shade on the performance of two tropical forage legumes: Centrosema molle (CIAT 15160) and C. macrocarpum (CIAT 5713). Acclimation to shade in these two species was investigated at individual leaf and whole canopies, to explain differences in the efficiency of radiation interception and use, and thus forage yield. Under 30% sunlight, midday leaf net photosynthesis (A) was reduced by 32%–44%, although instantaneous light use efficiency increased up to 44%–140%. Almost 50% increase in leaf specific area was accompanied by 61% in total chlorophyll content. From analysis of the light‐response curves, net photosynthesis at light saturation was only reduced (by 36%) in C. macrocarpum. Efficiency of chloroplast photosystem II (PSII) was unaffected by shade. Canopy structure for light interception was not modified by shade, although conversion into biomass and final yield were significantly reduced (40%–43%) in C. macrocarpum. Results are discussed in terms of factors affecting potential acclimation to shade and the agronomic implications of using both forage legumes in mixed pastures under tree canopies.

Soil properties rather than plant production strongly impact soil bacterial community diversity along a desertification gradient on the Tibetan Plateau

“…In the early stage of desertification, plants always distribute more biomass to belowground to avoid increasing damage as the degree of disturbance increases (Holland et al, ; Wilson, Strickland, Hutchings, Bianchi, & Flory, ). This strategy is an important defense strategy for plants to resist external disturbances, especially in terms of grassland degradation caused by overgrazing (Byrnes, Eastburn, Tate, & Roche, ; Guenni, Romero, Guedez, Guenni, & Pittermann, ; Sun, Ma, & Lu, ). As the degree of desertification increased, aboveground and belowground biomass decreased significantly, indicating that desertification led to a significant decline in production functions.…”

Efeito Do Ambiente Luminoso Em Forrageiras De Clima Tropical Em Sistemas Silvipastoris

“…Para espécies forrageiras de clima temperado como a Centrosema (DC.) Benth, os pontos de saturação lumínica foram de 600 -1000 µmol m -2 s -1 (GUENNI et al, 2017).…”

“…Marandu. Guenni et al (2017), relataram que plantas de Centrosema macroporum quando submetidas a um sombreamento de 70% (30% de RFA do PS), tiveram a capacidade fotossintética reduzida e aumento de 13 para 18 mg g -1 da massa seca (38,5%) na produção de clorofila b nas plantas sombreadas. A clorofila b absorve a luz em espectros com menor comprimento de onda e em condições de sombreamento pode haver maior produção desse pigmento pelas plantas em resposta a absorção de RFA alteradas pela presença das árvores (LOPES et al, 2017b;NASCIMENTO et al, 2019).…”

“…Os fatores ambientais influenciam as características morfogênicas das plantas, como: taxa de alongamento de colmo, taxa de alongamento foliar, taxa de aparecimento das folhas e o tempo de vida das folhas (GUENNI et al, 2017). Essas características morfogênicas, por sua vez, vão afetar as características estruturais, como: relação folha: colmo; tamanho final da folha; DPP e número de folhas por perfilho (Figura 1).…”

“…Quando a luz utilizada no desenvolvimento das espécies vegetais é limitada, as respostas morfofisiológicas das forrageiras são alteradas (PACIULLO et al, 2011) na tentativa de aproveitar o máximo dos recursos naturais disponíveis. As mudanças nos padrões de respostas das plantas são estimuladas pela intensidade das alterações da luz solar incidente (SANTOS et al, 2016;GUENNI et al, 2017). Contudo, diversos mecanismos adaptativos a diferentes níveis de sombreamentos são relatados na literatura para que as espécies forrageiras consigam se manter produtivas.…”