Journal of Agriculture and Industry of South Australia, Volume 2: 868 (May 1899)

UNRIPE SEEDS.

The Hon. Secretary read an article from the Melbourne Leader on growing plants from unripe seeds, as follows:—

*Am. Nat. 29: 804-815, 904-913. 1895

Some time ago Mr. J. C. Arthur published in the American Naturalist an interesting paper on "Deviation in Development Due to the Use of Unripe Seeds."* That unripe seeds could germinate was known to Theophrastus 300 B.C., and has been the subject of investigation by many observers since. The author gives a very complete list of references to experimenters, alluding, among later ones, to Duhamel in 1760 (with ash and walnut), to Senebeir in 1800 (peas), and to Seffyer, 1822. This last observer took unripe green fruit of Sophora japonica, dried it, and obtained 500 young plants, though, as a rule, the plant does not ripen its seed in Germany. He also refers to the exhaustive treatise of F. Cohn in 1847, entitled "Symbola ad Seminis Physiologiam," in which that author reviews the previous history, and records results of his own experiments with more than twenty widely different species, raised from seeds in various stages of immaturity.

After discussing the disputed question as to what constitutes actual maturity, he quotes Nobbe's statement as representing the present usage:—"The continued life of the embryo is not dependent upon the completion of the storing of reserve material in the seed; the power of germination appears much earlier, even in a stage of development of the seed undoubtedly to be designated 'unripe.'" The author then proceeds to give statistics from several experiments. Thus—"Goff, in 1884, planted tomato seed in March in boxes in the green house, saved the previous season from fruit still thoroughly green, and obtained only 2 per cent. of vegetation. But of seed from fruit of full size, which has begun to lose its green color, although not showing any tinge of redness, as many as 84 per cent. vegetated, while from fruit with a faint reddish tinge the percentage of vegetation reached 100." "Nobbe found that seed of spruce fir (Picea vulgaris) gathered on the 1st and 15th of each month, from the middle of July to November 1st, and tested in the laboratory in the following January, gave increased percentages of germination according to degrees of maturity." The percentages rose from 0, when the seed was gathered on July 15th, to 40.8 on August 1st, to 76.3 on September 1st, and to 88.2 on November 1st."

After recalling the fact that fruit may ripen after the bough which bears it has been removed from the tree, he adds that Cohn first observed that green seeds entirely removed from the fruit and laid in moist earth or sand, passed through the various changes of color of normal ripening. He experimented with seed of apple, pear, beans, lupins, &c. Lucanus corroborated this fact with rye, showing that the weights of grain continued to increase, as the latter was left in the ear alone without the stalk; in the ear still upon the cut stalk; and lastly, with the roots in water. The general result is that there is an optimum period for germination, as over-ripening is as harmful as under-ripening, since all grains after a longer and shorter time lose their power of germination. Passing on to the effects, the first and most obvious in the germination of unripe seeds is the weakness of the plants and their undersized condition. Many perish by failing to rise to the surface of the earth. The rate of germination is also slower than the normal. Thus with wheat, of fifty grains, twelve still with milk germinated on the eleventh day; of grains turned yellow, nineteen had appeared in the same time; while of fully ripe grains, twenty-five had appeared. "Owing to their weakened condition, the plants from immature seed are less able to withstand unfavorable conditions than those from ripe seed, the difference being more marked the younger the seeds. In my own attempts to grow very green tomato seeds in the greenhouse fully 85 per cent. of the plants that had unfolded the cotyledons, perished before reaching the third leaf." Similarly for winter rye, Wollny raised 41 per cent. from very green grain, 91 per cent. from grain in the milk, and 100 per cent. from pale yellow and from fully ripe seed.

The author conducted experiments with tomatoes, and although the appearance of fully grown plants did not always show their deficiencies their weights revealed the fact that they had never recovered the ill effects of the unripeness of the seeds when first they germinated. Thus plants raised from the seed gathered from green fruit gave the average weight of a single fruit in grms., l7.5; from half ripe fruit, l7.9; and from fully ripe fruit, 19.4. These were calculated from 1,044, 439, and 1,889 ripe fruits respectively. From comparative results of growths, "without going into further details, the general principle may be stated, that plants from green seed will, as a rule, attain a smaller development in both vegetative and reproductive parts than those from ripe seed." But "the use of immature seed increases the reproductive parts at the expense of the vegetative, and thus it comes about that there is more fruit formed in proportion to the amount of foliage than normally."

As the result of the cumulative effect. of repetition through several generations it was found that a tomato plant, selected as representative of the series grown from unripe seed, bore 3 1/2 lb. of fruit to 1 lb. of leaves, stems, and roots taken together; while a plant of the same variety, grown each year under the same conditions, but always from ripe seed, gave only l 1/8 lb. of fruit for each lb. of plant. . . . . With this increased fruitfulness is also associated an increase in the number of fruits, although they are individually smaller, as also are the seeds.

*There is some reason to believe that in the case of certain cultivated vegetables unripe seeds may give rise to earlier varieties than come from ripe seeds. For numerous citations from the extensive literature of the subject see a paper by the author in the Report of the Secretary of the Massachusetts Board of Agriculture for 1878.
[Goodale, G. L.: Recent researches on seeds. Ann. Report Mass. Board of Agriculture, 1878, Part 1, pp. 262-284.]

Another feature of importance is the tendency to an increased earliness in ripening the fruit on plants raised from immature seeds. "In the cumulative trials of tomatoes by Goff, just referred to, the strain from green seed ripened from ten to four weeks earlier in different years than the corresponding series from ripe seed." The author supplies a table showing (in Goff's experiments of fifty seeds taken from each of the following stages of maturity), the number per cent. which vegetated, and the number of days before the first ten fruits were ripe, as follows:—From very green fruit, 2 per cent., 137 days; from pale green, 84 per cent., 157 days; from fruit tinged red, 100 per cent., 152 days; from light red fruit, 96 per cent., 147 days; from deeper red, 88 per cent., 147 days; from fully ripe fruit, 96 per cent, in 152 days. "This is not surprising in view of the fact that it is the weaker plants from which the greater earliness in fruiting is expected. . . . . It was noted by Goodale* in 1885, and since by Goff, that some early market variety of vegetables indicated that they may have been originated from the use of green seed."

The author then summarises the results under the following heads:—"1. There is a loss of vigor shown in the smaller percentage of germinations, the weakness of the seedlings and the greater number of plants which die before maturity. 2. The full vigor of the plants is never recovered, although they may, and usually do, produce an abundant harvest, and one acceptable to the cultivator, in case of economic plants. 3. The reproductive parts of the plants are increased in proportion to the vegetative parts, resulting in a greater number of fruits and seeds (although individually smaller), and more rapid ripening of them than in similar plants from mature seed." The general interpretation he expresses in the following sentence:—"The deviation in development which comes from the use of unripe seed does not differ in kind from that resulting from any other method of weakening the organism. It is only a special instance of the effect of checking the uniform normal growth of the individual."

It has been long known that analogous results acrue from using very old seeds, as in the case of the melon. Thus, M. F. Cazzuola found that melons raised from fresh seed bore a larger proportion of male flowers than female, while older seed bore more female flowers. M. Triewald grew twenty-one out of twenty-four melon seeds which were 41 years old. The branches were very slender, yet they produced both early and plenty of good melons.

"The retardation of the germination due to age is well shown by the tests of tomato seeds made by Lovett, in which seeds from 2 to 6 years old showed the first germination in 10 days; 7 years, in 11 days; 8 and 9 years in 12 days; 10 and 11 years, in 14 days; and 13 years, in 11 days. It will be observed that the effect of over-immaturity is the same as results from immaturity, . . . It is evident, therefore, that ageing as well as immaturity of seeds leads to weakness of the seedlings and a general lowered vitality."

Practical results may he deduced, which may be left to the experimenter to carry out, with such garden plants as are cultivated for their fruits. Like experiments should be made to test the effect of immaturity of the seeds upon plants —e.g., annuals—cultivated solely for their flowers, but for plants of which the roots, stems, and foliage are desired, it would seem that fully ripe seeds should always be chosen. For fruits, at least, it is quite evident that the cultivator may look for larger and earlier crops, though of diminished size, when immature seeds are used.