Seed Longevity and Deterioration

Abstract

The fundamental deteriorative processes that lead to loss of seed viability contrastingly vary between desiccation insensitive (orthodox) and desiccation sensitive seeds (recalcitrant). Orthodox seeds which undergo maturation drying are bestowed with protective mechanisms which guard the seeds against deterioration. They include the accumulation of antioxidants, non-reducing sugars, protective proteins such as late embryogenesis abundant proteins, heat-shock proteins, lipocalins, hormones and chemical protectants (raffinose family oligosaccharides, flavonoids, lignins, vitamin E). The nuclear DNA is packed denser and chlorophyll is degraded. Besides, the cytoplasm is capable of transitioning between liquid and glassy state depending on the moisture content of the seeds aiding in the maintenance of seed viability potential. In the dry seeds, the glassy state of the cytoplasm ensures the stabilization of cellular components by arresting cell metabolism. However, even with low moisture content and a glassy state of cytoplasm, reactive oxygen species generated due to the presence of oxygen in the storage atmosphere may cause the ageing of seed. As the seed moisture content increases, mitochondrial respiration gets activated, also leading to increased production of reactive oxygen species, owing to inefficient mitochondrial activity. The reactive oxygen species lead to the oxidation of essential molecules such as DNA, RNA, proteins and lipids. Further, mitochondrial membranes also get oxidized, leading to reduced aerobic respiration potential. When the damage is not substantial, orthodox seeds are capable of repairing the molecular damages that accumulate during storage, enabling the seeds to partially overcome the damages and extend their longevity. This includes activation of repair of cell membranes, DNA, RNA, proteins and mitochondria as the seeds imbibe water.Unlike the orthodox seeds, the recalcitrant seeds are largely devoid of protective mechanisms which guard the seeds against rapid deterioration. The recalcitrant seeds are shed from the mother tree at high moisture content while they are metabolically active. After dispersal, the seeds undergo deteriorative changes during drying due to the damage to the cytoskeleton (physical damage), besides reactive oxygen species-induced damage due to lack of antioxidant activity (metabolism-induced damage). Even when maintained under high moisture content, seeds exhibit dysfunction of the cell organelles and extensive vacuolization predisposing the seeds to deterioration. Thus, recalcitrant seeds are prone to deterioration either under low or high moisture content.

Seed resurrection study unearths evolution of phenotypic plasticity

“…A noteworthy characteristic of wetland soils is the anoxic conditions that develop under waterlogged conditions. These conditions limit decomposition of plant biomass and facilitate long-term preservation of seed viability (Ranganathan & Groot, 2023). Vahsen et al (2023b) utilize this preservation to achieve a truly innovative experimental design: resurrecting century-old seeds and comparing them with descendent plants from seeds higher in the soil profile (Fig.…”

“…A noteworthy characteristic of wetland soils is the anoxic conditions that develop under waterlogged conditions. These conditions limit decomposition of plant biomass and facilitate long‐term preservation of seed viability (Ranganathan & Groot, 2023). Vahsen et al .…”

PGRFA Management of Outcrossing Plants Propagated by Seed: From On-Farm to Ex Situ Conservation and Some Italian Maize Case Studies

“…A safe moisture level for field collection is around 50% equilibrium relative humidity (eRH) [53], then the seed moisture content is reduced to the recommended levels for storage, using techniques that are not detrimental to seed viability [56]. It is known that when seed moisture content is between 5% and 14%, each 1% decrease in seed moisture doubles the shelf life of the seeds [57,58].…”

Insights into mechanisms of seed longevity in soybean: a review

“…Furthermore, they help in stabilization of glassy cytoplasm, protection of structural proteins, condensation of chromatin and dismantling of thylakoids in chloroplasts (Sano et al, 2015;Ballesteros et al, 2020) Increased number of transcripts encoding HSPs and heat shock factors (HSFs) offer resistance against accelerated ageing in soybean (Lima et al, 2017). Defensive proteins like polyphenol oxidases, peroxidases and chitinases playing a protective role, accumulate in soybean seed testa during stress (Ranganathan and Groot, 2023). Protein content of soybean seed from all nodal positions decreased vastly after 180 days of storage leading to deterioration in longevity (Sharma et al, 2013).…”