Deterioration Resistance Mechanisms in Seeds

Hubungan Antara Kandungan Lignin Kulit Benih Dengan Sifat-Sifat Khusus Kulit Benih Kacang Hijau

“…Lebih lanjut beberapa peneliti mengemukakan bahwa benih kedelai yang resisten terhadap deraan cuaca umumnya memiliki permeabilitas kulit benih yang rendah (low seed coat permeability) (Marwanto, 2003c;Dassou and Kueneman, 1984) ataupun kulit benih yang keras (hard seed coat) (Dassou and Kueneman, 1984;Kuo, 1989). Menurut Halloin (1983) kulit benih sebagai faktor penentu permeabiltas berfungsi (1) sebagai penghalang mekanis (mechanical barrier) sewaktu benih menyerap air (moisture) dari udara sekelilingnya yang lembab akibat sifatnya yang higroskopis, dan (2) sebagai penghalang (barrier) terhadap merembesnya elektrolit (electrolyte leakage) dan keluarnya senyawa-senyawa dari dalam benih seperti gula melalui kulitnya sewaktu benih berada dalam udara yang lembab maupun media basah lainnya. Menurut Tavares et al (1987) pada benih dengan permeabilitas rendah akan terjadi penyerapan air (imbibisi) yang lambat ataupun sebaliknya.…”

Rapid deployment of allelochemicals in exudates of germinating seeds of Sesbania (Fabaceae): roles of seed anatomy and histolocalization of polyphenolic compounds in anti-pathogen defense of seedlings

“…During days 1-3, flavonoids occurred in sig- We suggest that this parenchyma functions as an anti-pathogen ''filter'' between the lens, where water enters the imbibing seed, and the radicle. The dormant seed is protected by dehydration from all biological activity (Vertucci and Roos 1990), and by the impermeable seed coat from the pathogens ubiquitous in its environment (Halloin 1982(Halloin , 1983Harman 1983). When the dormant seed becomes permeable, its vulnerability is immediately increased.…”

“…The water that enters the lens may also bring pathogens that could quickly kill the seedling: indeed, micro-organisms are ubiquitous in soil as dormant propagules and rapidly respond to germinating seeds by breaking dormancy (Short & Lacy 1976;Venere 1980). Thus, breaking of dormancy by pathogens in response to exudation ensures rapid invasion of germinating seeds by hyphae (Halloin 1983;Harman 1983;Norton & Harman 1985;Nelson 1990). It is thus difficult for the seedling to avoid infection by fungal pathogens.…”

“…Pathogen attacks occur in the first hours of seedling development (Harman 1983;Nelson 1990), at a stage when the seedling is highly vulnerable because most resources are allocated to growth and are thus unavailable for defence (Sprent & Thomas 1984;Herms & Mattson 1992). These environmental pressures have shaped the structure of the seed coat, helping to ensure that dormant seeds remain viable during long periods of storage in pathogen-rich soils (Anderson & Baker 1983;Halloin 1983;Harman 1983;Graaff & Van Staden 1984;Kremer et al 1984;Cabrera & Martin 1986;Helsper et al 1994).…”

“…These interactions may be antagonistic (e.g., with pathogens) or positive (e.g., the symbiosis between legumes and rhizobia). Because pathogenic fungi, bacteria, viruses and nematodes are abundant in soil, seeds with long periods of dormancy require defence for their persistence in soil (Anderson & Baker 1983;Halloin 1982Halloin , 1983Harman 1983;Graaff & Van Staden 1984;Kremer et al 1984;Cabrera & Martin 1986;Helsper et al 1994). Upon germination of the seed, these pathogens may quickly kill young seedlings or weaken them at a critical and highly vulnerable stage of growth.…”