Hormones and Seed Development

Pesticides are only one group of chemicals in use in agriculture. There are now hormones either to accelerate or retard the growth of plants. Livestock are being fattened with the aid of chemicals. Soil and seeds are treated with chemicals. New fertilizers are being developed. Many other applications are being discovered. 

The seeds of fenugreek produced an antifertility effect in female rabbits and a toxicity effect in male rabbits (Kassem et al., 2006). Feeding diets containing 30% fenugreek seeds resulted in a reduction of testis weight in males and damage to the seminiferous tubules and interstitial tissues. In addition, the plasma concentration of the antrogen hormone and sperm concentrations was halved in treated animals. In the case of females, development of the fetus was reduced. 

There are two important classes of allelochemicals synthesized by oxidative cleavages of tetraterpene carotenoids. One is the plant hormone abscisic acid (ABA, 31) that plays important roles in growth and development of plants, especially in seed development and dormancy.17 Dry dormant seeds contain relatively large amounts of ABA, particularly in the seed coats. ABA and phenolic allelochemicals in the seed coats are easily released into the environment when the seeds are imbibed, resulting in inhibition of seed germination and seedling growth of plants in the vicinity. Both ABA and the phenolic compounds are rapidly broken down in the soil, and therefore the inhibition is short-lived. 

The phytohormone abscisic acid (ABA) plays an important role in many physiological processes in plants. This hormone is necessary for regulation of several events during late seed development [54,70]. Furthermore, ABA is crucial for the response to environmental stresses such as desiccation, salt and cold [10,39]. 

The roles of ABA in seed development and in response to drought, salt and cold stress are the most extensively studied effects of the hormone. However, ABA is also involved in other processes. ABA deficient mutants of potato and tomato show reduced response to wounding. Application of ABA can reverse the phenotype demonstrating the direct relationship between ABA and wound response [34]. Treatment of bromegrass cell cultures with ABA induces increased heat tolerance. At least four days of ABA treatment is needed to achieve tolerance. This effect of ABA is thus a slow response like the cold acclimation and induction of desiccation tolerance in C. plantagineum. 

Whether brought by the pollen or synthesized in the ovary or elsewhere in the plant and transferred to the growing embryo, hormones (obviously including GAs) seem to be fundamental for seed development. 

All of these results lead us to conclude that a very thorough future examination of the hormone-supplying role of the angiosperm suspensor could provide important insights into the understanding of both seed and embryo development. 

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