Exogenous Antioxidants Enhance Seedling Growth and Yield of Artificially Aged Cabbage and Lettuce Seeds

Ademola Adetunji,Sershen Sershen,Norman Pammenter,Boby Varghese

doi:10.3390/horticulturae7090274

Ademola Adetunji, Sershen Sershen + Show 2 more

Open Access

https://doi.org/10.3390/horticulturae7090274

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Abstract

Aged seeds exhibit compromised vigour in terms of germination, seedling emergence and growth, but this can to some extent be alleviated by invigoration treatments before sowing. This study aimed to investigate ageing rates and patterns in cabbage (Brassica oleraceae) and lettuce (Lactuca sativa) seeds and whether the beneficial effects of invigorating aged seeds with exogenous antioxidants translate to enhanced seedling performance. Seeds were artificially aged to 25% viability before soaking in 0.4 mM glycerol, 0.6 mM GSH and 0.2 mM trolox for cabbage, and 0.6 mM glycerol, GSH and trolox for lettuce; deionised water served as a control. After 14 days of sowing, seedling emergence percentage, mean emergence time, mean daily emergence, and time taken to 25% emergence were computed. Seedling vigour index, root and shoot dry weight, root:shoot ratio, leaf area, leaf area ratio, and leaf chlorophyll content were assessed 6 weeks after sowing. Furthermore, the photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), and chlorophyll fluorescence were measured 6 weeks after sowing. Notably, ageing resulted in the loss of seed vigour and viability at higher rates in lettuce than cabbage. Seed pretreatment with glycerol promoted seedling growth in both species and shoot dry weight in lettuce, while glycerol and GSH enhanced Pn, Gs and E in lettuce. Trolox also enhanced Pn and E in lettuce. The beneficial effects of the antioxidant treatments are thought to be associated with the protection of photosystems from oxidative stress and/or stimulation of enzymes involved in photosynthesis, possibly through an enhanced antioxidant defence system during the early development stages when seedlings are particularly vulnerable to stress.

Highlights

Seeds are continually faced with multiple challenges relating to production, postharvest storage, and subsequent quality
The asymptomatic phase was followed by a progressive decline in normal seedling production, with seeds reaching P75, P50, and P25 more or less on days 6, 13, and 17, respectively
This study showed that seed ageing resulted in the loss of vigour and viability in both species but at different rates

Summary

Introduction

Seeds are continually faced with multiple challenges relating to production, postharvest storage, and subsequent quality. In view of the effects of global warming as a symptom of climate change, different stress factors may cause poor seed performance in terms of reduced germination, uneven seedling emergence, poor seedling establishment, destructive alteration of root cell architecture, and thereby leading to a substantial yield loss [1]. Standard germination assessments can be used to predict the actual field performance of seeds [2], but the predictions of subsequent establishment and growth are not entirely reliable [3]. Especially in agricultural seeds, requires good emergence and establishment of seedlings for maximal yield. Studies have indicated differences in seed performance under optimal laboratory conditions compared with field conditions, which are rarely optimal. Emergence rate, and shoot fresh and dry biomass have been reported to be higher in pre-hydrated caraway

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