Characterization of volatile production during storage of lettuce (Lactuca sativa) seed

Abstract

The duration that seeds stay vigorous during storage is difficult to predict but critical to seed industry and conservation communities. Production of volatile compounds from lettuce seeds during storage was investigated as a non-invasive and early detection method of seed ageing rates. Over 30 volatile compounds were detected from lettuce seeds during storage at 35 degrees C at water contents ranging from 0.03 to 0.09 g H(2)O g(-1) dw. Both qualitative and quantitative differences in volatile composition were noted as a function of water content, and these differences were apparent before signs of deterioration were visible. Seeds stored at high water content (L >or=0.06 g H(2)O g(-1) dw) emitted molecular species indicative of glycolysis (methanol+ethanol), and evidence of peroxidation was apparent subsequent to viability loss. Seeds containing less water (0.03-0.05 g H(2)O g(-1) dw) produced volatiles indicative of peroxidation and survived longer compared with seeds stored under more humid conditions. Production of glycolysis-related by-products correlated strongly with deterioration rate when measured as a function of water content. This correlation may provide a valuable non-invasive means to predict the duration of the early, asymptomatic stage of seed deterioration.

Volatile fingerprints of seeds of four species indicate the involvement of alcoholic fermentation, lipid peroxidation, and Maillard reactions in seed deterioration during ageing and desiccation stress

“…Acetaldehyde was also produced in relatively large amounts by all species, with the exception of C. scoparius . These four compounds have been widely reported in other studies of seed volatile production during storage (Zhang et al ., 1993, 1995 a ; Buckley and Buckley, 2009; Mira et al ., 2010). In this investigation, analysis with the Tenax adsorbent showed that ethanol production was inversely correlated with germination for P. sativum and Q. robur seeds following ageing and desiccation, respectively (Table 1).…”

“…The headspace can be sampled directly using a gas-tight syringe (Zhang et al ., 1995 a ; Mira et al ., 2010) or the volatiles can be concentrated using an adsorbent trap, for example Tenax, a polymer resin (Zhang et al ., 1993). Solid phase microextraction (SPME) uses an adsorbent fibre within a syringe.…”

“…Solid phase microextraction (SPME) uses an adsorbent fibre within a syringe. The fibre is exposed to the headspace within a vial, and the trapped volatile compounds are then transferred to a GC-MS by thermal desorption (Tholl et al ., 2006; Mira et al ., 2010). The above sampling techniques have all been used previously in studies of seed volatiles, but there are few reports of comparison between the techniques.…”

Biochemical changes induced in seeds of Brassicaceae wild species during ageing

“…Arrow corresponds to the point at which germination decreased to 80% of maximum germination (Kibinza et al 2006;Murthy et al 2003;Walters 1998). The study of the production rate of volatile peroxidation by-products by lettuce seeds during storage demonstrates that the deterioration mechanisms involved in viability loss differ depending on seed water content (Mira et al 2010a). In sunflower seeds, viability loss was associated with lipid peroxidation only when the water content of the embryo axis was higher than 0.30 g H 2 O g -1 DW (Kibinza et al 2006).…”

Orthodoxy, recalcitrance and in-between: describing variation in seed storage characteristics using threshold responses to water loss

“…Shifting positions of ligands through vibration or rotational motion can create the opportunity for reaction among molecules in close proximity. Hence, the structure and mobility of molecules within glasses explains discrete changes in reaction kinetics as glasses plasticize (Vertucci and Leopold 1987;Vertucci and Roos 1990;Mira et al 2010;Colville et al 2012). One can imagine sophisticated regulation of some types of reactions by diversifying glassy structure within different regions of the cell or seed.…”