in Genetics pp. 4-5 (1956)
Metabolism and Spontaneous Mutations in Plants
Francesco D'Amato, Instituto di Botanica dell'Università, Pisa Italy,
and Otto Hoffman-Ostenhof, Erstes Chemisches Laboratorium der Universität, Vienna, Austria
2. Remarks on Some Morphological and Physiological Aspects of Seed Aging
It has been known for some time that plants grown from aged seeds frequently show retarded growth and aberrations in their development. As early as the seedling stage, the following aberrations have been observed:
(a) In various Crepis species (Nawashin, 1933; Nawashin and Gerassimova, 1936a,b) as well so in Pisum sativum (D'Amato, 1953a,b), necrosis of the meristems of the radicle; in Pisum the meristems may be completely suberized.
(b) In the same plant species, occurrence of adventitious roots from the hypocotylar and/or epicotylar regions and, less frequently, from the stump of the atrophied radicle.
(c) In Antirrhinum majus (Stubbe, 1935a), in Crepis species (Nawashin and Gerassimova, 1936a), in Oenothera berteriana (Schwemmle, 1940), in Nicotiana tabacum (Gisquet et al., 1951), in Nicotiana rustica (Scarascia and Venezian, 1953), and in Pisum sativum (D'Amato, 1953a,b), early death of the seedlings.
As for plants raised from aged seeds, the following aberrations have been reported:
(a) In Oenothera campylocalyx, Schwemmle (1952) observed a statistically significant reduction of the size of the leaves, sepals, and petals, and later a decreased mean height of the mature plants. A reduction in the vegetative development has also been reported of plants raised from aged seeds of maize, garden pea, barley, wheat, and soybean (for reference, cf. D'Amato, 1954). The phenomena of reduced growth observed in all these cases seem to have much in common with the changes in morphological and physiological characteristics in vegetative plant parts, occurring in some species as a symptom of meristem aging (cf. Ashby and Wangermann, 1954). As pointed out by Mather (1954) and by D'Amato (1954), detailed investigations of these phenomena might greatly contribute towards our understanding of the changes taking place during development and aging.
(b) In wheat (Schkwarnikow, 1937) and in tobacco (Gisquet et al., 1951), reduced fertility has been found; Avery and Blakeslee (1936, 1943) observed pollen abortion in Datura.
(c) In tobacco, wheat, and maize, changes in shape and appearance of some vegetative parts, including chlorophyll defects, have been described (for reference, cf. D'Amato, 1954); Peto (1933) has reported chlorophyll defects of the "striata type" in maize, which were phenotypically similar to those obtained by Stadler (1930) in maize plants raised from X-ray-treated seeds.
In connection with the well-known phenomenon of the decrease and loss of seed germinability, occurring at different times according to the species and to the external conditions, some interesting phenomena have to be discussed. When we study the course of germinability in relation to duration of storage in seeds with a short or medium life span, after a certain time, a sudden and pronounced decrease of germinability can be observed in many cases. Some examples of such a behavior are to be found in Tables 17 and 18 of the book of Crocker and Barton (1953); a few further illustrative cases will be mentioned here:
In the homozygous strain 50 of Antirrhinum majus, Stubbe (1935a) found a decrease of the germination rate of the seeds from about 73% to 26% between the ninth and the tenth year of storage. According to Crocioni (1934), seeds of Brassica campestris var. oleifera, stored for 5 years, still showed a germination rate of 88%, while after 6 years, germinability had decreased to 1%. In Nicotiana tabacum, Gisquet et al. (1951) found that seeds of the 1945 crop, stored under laboratory conditions at the Bergerac Tobacco-Breeding Station, kept normal germinability up to the end of 1948; during 1949, a rapid decrease of the germination rate took place (March, 25%; July, 9%; end of August, 1%).
CybeRose note: The highlighted text above may explain the traditional value of old seeds of melons, cucumbers, balsams, cabbages, turnips, etc. The seedlings of old seeds are physiologically older than seedlings raised from fresh seeds. Thus, traits associated with maturity (flowering or heading or bulbing) occur earlier.
As for the similar performance of some plants raised from unripe seeds, it may be that the rejuvenation of the meristem is not completed, and therefore the seedlings are also physiologically older.