Within-plant variation in concentrations of amino acids, sugar, and sinigrin in phloem sap of black mustard,Brassica nigra (L.) Koch (Cruciferae)

Abstract

Abstract--Although within-plant variation in the nutrient and allelochemical composition of phloem sap has been inw)ked to explain patterns of host use by phloem-feeding insects, little is known about within-plant variation in phloem chemistry. Here 1 describe a new technique in which 1 use the green peach aphid, I¢l~':us pe~wicae Sulz., to investigate within-plant variation in the concentrations of chemicals in the phloem sap of black mustard, Brassica nigra (L.) Koch (Crucilerae). Relationships between the concentrations of chemicals in aphid diets and honeydew were established using honeydew from aphids led on artificial diets with known concentrations of amino acids, sucrose, and sinigrin. These relationships were applied to honeydew from aphids led on different aged leaves of black mustard to estimate the concentrations of the chemicals in phloem sap, Sinigrin concentration was estimated to be high ( > 10 mM) in phloem sap in young leaves, calling into question the prevailing opinion that phloem sap contains only low concentrations of allelochemicals. High concentrations may function as defenses against sap-feeding herbivores. Within-plant variation in phloem sap composition was high: (I) young leaves had high concentrations of nutrients (216 mM amino acids, 26% sugar) and sinigrin (> 10 mM); (2) mature and presenescent leaves had lower concentrations of nutrients (77-83 mM amino acids, 19-20% sugar) and low concentrations of sinigrin (1-2 raM); and (3) senescing leaves had high concentrations of nutrients ( 199 mM anaino acids, 25% sugar) and low concentrations of sinigrin (3 raM).

The cabbage aphid: a walking mustard oil bomb

“…Despite this difference in body weight, aphids sequestered similar levels of sinigrin (on a nanomoles sinigrin per milligram aphid basis) whether feeding on a 1% sinigrin artificial diet or B. nigra. The sinigrin concentration in B. nigra phloem sap has been estimated at greater than 0.4% (Merritt 1996) and it is probable that the two experimental systems in this study (plants and artificial diets) presented aphids with approximately equal dietary sinigrin concentrations.…”

Evaluation of automated sample preparation, retention time locked gas chromatography–mass spectrometry and data analysis methods for the metabolomic study of Arabidopsis species

“…Sucrose concentrations also varied between the younger and older Arabidopsis samples. This observation was a good proof of within-plant variation in concentrations of sucrose [31].…”

Variation in glucosinolates in pak choi cultivars and various organs at different stages of vegetative growth during the harvest period

“…The correlation between GS concentrations in the shoots and roots may be due to the transport of GSs or their precursors through the phloem and also may be a part of the plant's defense system (Zangerl and Bazzaz, 1993;Merritt, 1996;Brudenell et al, 1999; Chen and Andreasson, 2001;Grubb and Abel, 2006). The correlation and independence of GS compositions between the shoots and roots could be of value to breeding programs for agricultural practice.…”