Respostas na germinação e no crescimento inicial de rabanete sob ação de extrato aquoso de Piper mikanianum (Kunth) Steudel

Abstract

ABSTRACT(Responses in germination and early growth of radish under the infl uence of an aqueous extract of Piper mikanianum (Kunth) Steudel). Th is study evaluated the allelopathic eff ects of an extract from P. mikanianum leaves on the germination and early growth of radish (Raphanus sativus L.). Leaf extracts were prepared at concentrations of 2, 4 and 8%. Th e pH and osmotic potential of the extracts were determined. Germination bioassay consisted of fi ve replicates of 25 radish seeds distributed in Petri dishes with germitest paper and 7 mL of extract or water, and were kept at 25°C in B.O.D. for fi ve days. Germination percentage (PG), germination speed (VG), germination speed index (IVG) and index of allelopathic eff ect (RI) were determined. For bioassay initial growth, seeds were germinated until the protrusion of the radicle was 2 mm and transferred to Gerbox boxes containing germitest paper and 15 mL of extract or water, which were kept for seven days at 25°C in B.O.D. to evaluate the length of the radicle and hypocotyl, fresh and dry mass, water content and chlorophyll content (a, b and total). Leaf extracts from P. mikanianum negatively aff ected all parameters examined for germination (PG, VG, IVG and RI). Th e extracts aff ected the initial growth, causing reduction of the radicle length and stimulating the growth of the hypocotyl. In addition, the extracts at 8% concentration reduced fresh weight and water content. Extracts at concentrations of 2 and 4% increased the content of chlorophyll b and total chlorophyll. Th us, Piper mikanianum exerted an allelopathic eff ect on radish.

Allelopathic Potential of Hesperozygis ringens Extracts on Seed Germination of Soybeans and Beggarticks

“…For the germination speed index, the results demonstrate a significant reduction in the number germinated seeds per day in relation to the control, for both species ( Figure 1D). Similar results were observed by Borella et al (2012), who used extracts from Piper mikanianum (Kunth) Steudel leaves on the germination of radish seeds that influenced the GSI, a response that depended on the dose used.…”

Compostos Bioativos Em Flores Comestíveis

“…Os compostos bioativos, que estão presentes em todas as partes dos vegetais, são em sua maioria, produtos do metabolismo secundário das plantas, e apresentam funções de atração de polinizadores e disseminadores de sementes além de exercerem importante função na proteção contra estresses bióticos e abióticos (BORELLA et al, 2012).…”

Biochemical analysis, photosynthetic gene (psbA) down–regulation, and in silico receptor prediction in weeds in response to exogenous application of phenolic acids and their analogs

“…Formation of one and two hydrogen bonds with FA and GA respectively, as depicted with docking analysis, predicts its plausible involvement in inhibition of photosynthetic activity and ultimately the weed growth. The two amino acids (his-198 and thr-286) depicting binding affinity with FA and GA, are different from the ones that are known targets of PSII inhibtor herbicides (ser-264 and his-215) and have reported to developed resistance in weeds [18,36]. Prediction of unexplored sites of action with FA and GA thus provides opportunity to cope with continually increasing herbicide resistance in weeds by employing naturally derived compounds.…”