Interactions Involving Allelopathy in Cropping Systems

Abstract

Allelopathic inhibition typically results from the combined action of a group of allelochemicals which, collectively, interfere with several physiological processes. The objectives of this paper are to summarize research that illustrates the joint action of allelochemicals, and to provide evidence that both the amount and detrimental action of these compounds depends on the extent of associated abiotic and biotic stresses. Allelopathy is strongly coupled with other stresses of the crop environment, including insects and disease, temperature extremes, nutrient and moisture variables, radiation, and herbicides. These stress conditions often enhance allelochemical production, thus increasing the potential for allelopathic interference. In the paradigm of interactions, the data indicate that crops are more sensitive to allelopathy when moisture, temperature, or nutrient conditions are less than optimal. For example, the inhibition threshold concentration for ferulic acid to affect seedling growth was reduced with even minor moisture stress (Ψ = − 0.15 MPa) or a growth temperature at the higher end of the normal range for a species. Under greenhouse conditions, additive inhibition resulted from the joint action of ferulic acid with low levels of alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], atrazine [6‐chloro‐N‐ethyl‐N’‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], or trifluralin [2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoromethyl)benzenamine]. Interactions of multiple stresses in crop environments will determine the relative impact of allelopathy. Allelopathystress interactions also have implications for herbicide and residue management strategies, crop rotations, biological control measures, and tillage practices that can contribute to a more sustainable agriculture.

Determinação de espécie indicadora e comparação de genótipos de girassol quanto ao potencial alelopático

“…Plantas liberam no ambiente diversos compostos do metabolismo secundário (Einhellig, 1996). Os efeitos observados pela utilização da semeadura em substituição, resultantes do convívio entre plântulas, provavelmente são devidos à liberação de compostos alelopáticos -alguns com maior e outros com menor atividade sobre espécies indicadoras.…”

Chemical Composition and Phytotoxicity of Volatile Essential Oil from Intact and Fallen Leaves of Eucalyptus citriodora

“…In the leaf litter, however, the least content of oil [(2.36 ð 0.04) ml/100 g leaves] was determined and it was nearly half of that found in the juvenile or senescent leaves. Such variability in the content of essential oils (secondary metabolites) is not surprising as the amount of secondary metabolites changes with aging or metabolic state of the plant (Einhellig, 1996). Kong et al (2002) reported that the amount of volatile oils in Ageratum conyzoides increases under stress conditions.…”

Efeito alelopático de folhas de Solanum lycocarpum A. St.-Hil. (Solanaceae) na germinação e crescimento de Sesamum indicum L. (Pedaliaceae) sob diferentes temperaturas

“…Esses agentes alelopáticos são geralmente compostos secundários produzidos pelas plantas e liberados por lixiviação, volatilização, decomposição e exudados da raiz (Inderjit & Dakshini 1992;1994). A produção de compostos secundários pode ser aumentada por diversos fatores ambientais como estresse hídrico, deficiência de nutrientes e temperatura (Einhellig 1996) situações comumentes encontradas no Cerrado.…”