Improvement of Crop Production by Means of a Storage Effect
Abstract
This study summarizes the results of 30 years of our experiments with Vicia faba L seeds. Our long-term practical observations of different Vicia faba L. cultivars points out the method useful for the higher yield of seeds in terms of their viability and thus higher crop production.
Our experiments led to the following important findings regarding of seed viability:
1. Individual and group variability of seeds;
2. Storage condition before germination; and
3. The condition of their germination.
All these three influential conditions is possible to optimalize by method of storage effect described in this our report resulting in the improvement of crop production. This is especially important in case of seeds that are rare and/or expensive , i.e. se eds that are genetically modified or with rearranged karyotypes.
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Introduction
Seeds have been studied for more than hundred years (cf. Murín 2001; Murín and Mičieta 2009). The first reports uncovered the relationship between the decline of their vitality and their storage conditions (Navaschin 1933; Cartledge and Blakeslee 1934, 1935; Stube 1935; Nichols 1942; D’Amato 1951; Murín 1961; Avanzi etal. 1969). Since resp iration is the most marked manifestation of metabolism in stored seeds, it should also be considered. Rieger and Michaelis (1959) found that V. faba seeds are susceptible to the action of ethanol or other “automutagens” which can accumulate during there spiration of seeds stored over long period. Bewley and Black (1982 , 1994) explored the relationship between the color of the testa and the dormancy and germination of wheat, as affected by the level of inhibitors (catechinins and their derivates) occurring in the testa. Floris and Anguillesi (1974) made a major contribution to the understanding of this external manifestation of the internal state of broad bean seeds when they reported on several biochemical and functional changes in aging seeds. Over the course of long storage, enzymes like catalase, peroxidase, cytochrome oxidase and decarboxylase display diminished activity, while the protein-synthesizing capacity of older seeds is lost in the process of germination. Furthermore, membrane permeability increases, resulting in reduced sugars and other metabolic products.
According Roos (1980) four factors must be considered in seed storage – time, temperature, relative humidity (seed moisture content) and a level of oxygen. With the exception of recalcitrant species, two factors – time and oxygen level, have very little effect on storability if the optimum seed moisture content and storage temperatures are observed. For example, Roberts and Ellis (1977) predicted the 95% survival of pea ( Pisum sativum L.) se eds after 1,090 years of storage at-20°C and 5% seed moisture content. If the storage temperature is reduced further, the viability may be extended indefinitely. Attempts to prolong life of seeds during the storage were focused at the use of liquid nitrogen (LN2) as a storage medium with a temperature-196°C. At this temperature, presumably all biochemical activity is reduced to essentially zero. Thus the deteriorative changes noted above should be eliminated. According Babasaheb (2004), safe seed storage moisture should be less than 8%.
In 1981, King etal. reported that the survival of lemon ( Citrus limon L.), lime ( C. aurantifolia Swing.) and sour orange seeds (C. aurantium L.) was examined under a wide range of constant moisture contents and temperatures. Seed longevity was increased by decreasing the moisture content and temperature of the storage environment. Maximum viability was maintained in a combination of storage conditions including the lowest moisture content (5%) and lowest temperature ( - 20°C) . The practicality of the dry storage of citrus seeds for genetic conservation was pointed out.
Bonner (1990) offered classification of stored seeds into four classes of storage characteristics: „‘true orthodox’ seeds can be stored for long periods at seed moisture contents of 5 –10% and sub-freezing temperatures; ‘sub-orthodox’ seeds can be stored under the same conditions, but for shorter periods due to high lipid content or thin seed coats; ‘temperate recalcitrant’ seeds cannot be dried at all, but can be stored for 3 –5 years at near-freezing temperatures; and ‘tropical recalcitrant’ seeds also cannot be dried, and they are killed by temperatures below 10 –15°C."
Grilli et al. (1995) described the level of Poly ( A) Polymerase as a significant marker of the viability of seeds during their long term storage. Also, during imbibition the production of the major organic volatiles, ethanol and acetaldehyde, depends greatly on the long term storage of the seeds (Górecki etal. 1992). Murthy etal. (2002) identified two primary biochemical reactions responsible for deterioration of seed vigour during long term storage – lipid peroxidation and non-enzymatic protein glycosylation reducing sugars. The PCR analysis of Chwedorzewska etal. (2002) led the authors to the conclusion that long term storage of seeds causing the loss of their viability also generates heritable changes in the preserved germplasm. On the other hand, antioxidant activity in stored seeds under different conditions (temperature andw.c.) is not related to seed viability (Merritt etal. 2003). However, Andreev etal. (2004) found that the loss of germination during the storage of rye seeds was accompanied by a decreased excision of chromatin loop domains. As Patrick and Stoddard (2010) stated, “the large seed size of the faba bean has enabled this species to be a model for studies of the molecular physiology of seed development.”
The darkening of the testa of aging V. faba L. seeds and its manifestation has been a practical part of our work since 1988 (Murín 1988 a, b). Today we know that the color of the testa indicates the viability as well as theage of the seeds. Our goal was to study the relationship between the different storage conditions, the color of the testa of seeds and the viability of the seed samples.
Conclusion
In addition to the theoretical ramifications of our experiments, our work may also have practical implications in three fields:
1. As pointed out by Čupičetal. (2005), widely used agro-technical plant seeds, as in the case of Alfalfa ( Medicago sativa L.), are often stored for years after harvest, which influences their germination energy, germination, rate of abnormal sprouts and dead seeds. This can be easily repaired by the “storage effect” with an interrupted germination period under the described conditions causing the prolongation of the G-1 phase with a significant increase of vitality of seeds treated this way. Consequently, it will lead to an improvement of their crop production that is most important in the case of seeds that are genetically modified or rearranged (see ACB karyotype seeds used in our experiments).
2. Our findings may be very helpful to seed banks worldwide. The regular checking of the viability of seeds according to germination leads to irreversible losses of stored seeds, while a simple visual test based at seed color would provide the same answer with no loss of material. Moreover, such a test could be conducted in sealed ampules, thus not interfering with the storage conditions in the particular seed bank. By using “storage effect” these seeds can be revitalised (or rejuvenalised) and stored further with the possibility of long-term survival of the seeds in seed bank.
3. Finally, with the above mentioned “storage effect” the amount of yield of viable seeds can be significantly recovered and by this method to prolong of their useful survival in the particular agricultural supply. Just at the example of Vicia faba beans it could cause a significant economical improvement as its seeds are distributed in more than 55 countries when 4.56 million tons of dry grains are produced in the harvested area of 2.56 million ha yearly.
