Defoliation in Perennial Plants: Predictable and Surprising Results in Senna spp.

Abstract

When some plants are defoliated, they may suffer by reaching a smaller final size than if they had not been damaged. Other plants may compensate for damage, ending up the same size as if they had not been damaged. Still, others may overcompensate, ending up larger after defoliation than if they had been spared from damage. We investigated the response of Senna species (Fabaceae) to defoliation, comparing two native and several ornamental congeners, all of which grow locally in southern Florida. Many Senna spp. bear foliar nectaries as nutritional resources for beneficial insects that may, in exchange, protect them from herbivores. We grew five species from seed and subjected them to three levels of defoliation for a period of several months to measure effects of leaf area removal on plant height, number of leaves, and number of extrafloral nectaries. Only three of five species displayed shorter plant heights with greater levels of damage. Two species produced fewer new leaves with moderate to severe defoliation. In only one species, the number of extrafloral nectaries decreased with defoliation, suggesting that while extrafloral nectar production may be an inducible defense in some species, producing more nectaries in response to damage does not occur in these Senna species.

Is animal saliva a prominent factor in pasture regrowth?

“…plant photosynthetic capacity, root growth or nutrient uptake, the vast majority of cases does so without the added influence of saliva (Clement et al 1978;Parsons et al 1983;Jarvis and Macduff 1989;Christopher et al 2004) (Table 1). Additionally, while studies have investigated the role of defoliation only (Heady 1961;Jameson 1964;Harris 1978;Stroud et al 1985;Lindgren et al 2007;Deutsch et al 2010;Wang et al 2020Wang et al , 2022Koptur et al 2023), these studies ignore the potential impact that saliva has on stimulating plant growth (Reardon et al 1972;Detling et al 1980;McNaughton 1985;Teng et al 2010;Liu et al 2012) (Table 1).…”

Impacto de insetos herbívoros e do fogo no desenvolvimento vegetativo e reprodutivo de plantas de cerrado

“…Além disso, os tricomas constituem também uma excelente estratégia de defesa, dificultando a oviposição de insetos sobre as folhas (LEVIN, 1973) e com forma e função variadas ao longo da planta, além de poder desenvolver espessas paredes, ocasionalmente impregnadas com sílica ou carbonato de cálcio. Outros tipos de tricomas, os glandulares, armazenam terpenos, ácidos e outros compostos tóxicos, que agem como repelentes de insetos fitófagos (LEVIN, 1973). Os tricomas são bastante relacionados a adaptações para proteger contra o aquecimento excessivo da folha e perda de água por transpiração.…”