Growth and chemical defense in relation to resource availability: tradeoffs or common responses to environmental stress?

Abstract

One aspect of plant defense is the production of constitutive secondary compounds that confer toxicity on herbivores and pathogens. The purpose of this study was to compare patterns of plant tissue toxicity across gradients of irradiance and nutrient content. We measured the potential toxicity (1/LC50) of extracts of six species of herbaceous Asteraceae grown under controlled conditions of temperature (25 degrees C), humidity (80%), photoperiod (16 h/day), in a range of concentrations of a modified Hoagland hydroponic solution (full-strength, 1/5 dilute, 1/10 dilute, and 1/50 dilute) and under two different light intensities (250 and 125 micromol/m2/s). The plants grew from seed for 42 days post-germination, and randomly chosen plants were harvested each 7 days. We did a general measure of potential phytochemical toxicity using an alcohol extraction of secondary compounds followed by brine shrimp (Artemia sp.) bioassay. Contrary to the carbon/nutrient balance hypothesis, tissue toxicity generally increased with decreasing irradiance and nutrient levels, so that plants whose growth was most restricted had tissues that were most toxic, although there were species-specific differences in this trend.

Effects of nutrient availability on the production of pentaynene, a secondary compound related to defense, in Rudbeckia hirta

“…The full‐strength (1/1) solution has a nitrogen concentration of 3 mmol Ca (NO3) 2 .4H 2 O, 2 mmol NH 4 H 2 PO 4 , 5 mmol KH 2 PO 4 , 2 mmol MgSO 4 .7H 2 O, 9.07 µmol MnSO 4 , 0.765 µmol ZnSO 4 .7H 2 O, 46.4 µmol H 3 BO 3 , 0.09 µmol Na 2 MoO 4 .H 2 O, 0.01 µmol CuSO 4 plus 36 µmol FeSO 4 .7H 2 O as iron‐ethylenediamine tetraacetic acid (EDTA). The more dilute nutrient solution did reduce the growth rate of R. hirta in this experiment (Almeida‐Cortez 1997) and this has been found in independent experiments (Almeida‐Cortez et al . 1999, 2003).…”

Plant antiherbivore defenses in Fabaceae species of the Chaco

“…There are species that invest in given defenses according to resource availability (Almeida-Cortez et al, 2004;Hanley et al, 2007). Moreover defense mechanisms antiherbivore may complement each other, favoring the presence of mixed defense (Carmona and Fornoni, 2013).…”

Bioactivity evaluation against Artemia salina Leach of medicinal plants used in Brazilian Northeastern folk medicine

“…The first work in the use of A. salina bioassay was published in 1956, and thereafter, numerous articles have been reported in the literature on environmental studies, using natural products and toxins, including plant extracts (Nunes et al, 2009;Almeida-Cortez et al, 2004;Citó et al, 2003;Cavalcante et al, 2000;Lieberman, 1999). Many Natural Product laboratories have used this assay in their routines of isolation, purification and structural elucidation as an initial biologic screening technique, in order to select and monitor the phytochemical study of plant extracts in the search for bioactive substances (Almeida-Cortez et al, 2004;Siqueira et al, 1998).…”

“…Many Natural Product laboratories have used this assay in their routines of isolation, purification and structural elucidation as an initial biologic screening technique, in order to select and monitor the phytochemical study of plant extracts in the search for bioactive substances (Almeida-Cortez et al, 2004;Siqueira et al, 1998).…”