Juvenility vs Precocity

Janick et al: Juvenility in Apple Seedlings (1996)
Seedlings should continue to grow freely and, since the seedlings first come out of the juvenile condition at the top of the seedling, they should be left unpruned until they flower and fruit (Brown 1964; Zimmerman 1971). Tydeman and Alston (1965) have shown that the juvenile phase can be considerably shortened by budding seedlings onto dwarfing rootstocks. Buds were taken from the upper part of the main shoot in late summer of the second year's growth and worked on the dwarfing rootstocks 'M.9' and 'M.27', grown as closely planted cordons with all lateral growth pruned back annually in late summer. Nine years after germination 88% of 902 budded seedlings had fruited compared with 49% of those on their own rots. Virus-free rootstocks must be used to avoid infection.

Tayler: Germination of the Morning Glory (1906)
... plants grown in a green-house from immature green seeds blossomed earlier, had shorter stems and produced fewer seed-pods by about one-half than did those raised under the same conditions from seeds having no chlorophyll in the embryo. When the plants so grown from immature green seeds had ceased to blossom, those raised from mature colorless seeds were thrifty and still forming buds and maturing flowers and fruit. Both kinds of seeds were planted at the same time.

See also: Old Seeds / Unripe Seeds

Beaton: Influence of pollen in the same flower (1861)
In the great bulk of the Scarlet or Horseshoe Geraniums there are but seven stamens, four long ones, one of medium length, but which is often wanting, and two almost sessile like the anthers of Wheat—that is, very short indeed, and opening at the bottom face to face. These two are they which reduce a whole family to beggary; first to dwarfs or Tom Thumbs, or better still, to minimums, or the smallest of that kind consistent with vigour sufficient to become a useful plant in cultivation, and, lastly, to the brink of ruin, and drive that race out of existence altogether, if there were not other means provided to arrest the decline, or keep it from manifesting itself at all in a state of Nature.

Van Mons' System of Plant Breeding (1835)
All fine fruits are artificial products; the aim of nature, in a wild state, being only a healthy, vigorous state of the tree, and perfect seeds for continuing the species. It is the object of culture, therefore, to subdue, or enfeeble this excess of vegetation; to lessen the coarseness of the tree; to diminish the size of the seeds; and to refine the quality and increase the size of the flesh or pulp.

Burbidge: Precocity of some seedlings (1877)
It is very singular to note the precocity of some seminal varieties, and this tendency appears to be favoured by bad culture. Seedling Fuchsias, if starved, frequently flower when only an inch or two in height;

Viviand-Morel, On Different Ways of Striking Roses (1902/3)
Miller, the author of the "Gardener's Dictionary," in particular, after having mentioned striking, without saying how it was done in his time, adds: "Plants which are propagated from layers are less likely to throw out suckers than those which are taken from around old plants; hence they are to be preferred, as they take up less space and blossom more profusely."

Ball: Improvement of the grain Sorghums (1911)
Earliness can be developed only by continuous selection. Such selections can be made either at heading time or at the time of ripening, but are preferably the results of records made at both periods.

Michurin: Improving pear trees by layering (1929)
Then, after rooting by a method that I have devised, which even fruit growers of little experience can employ, the cuttings are planted in the bed when the leaves are fully developed. The cutting specimen bears fruit earlier than the seedling did. The cutting specimen of the second generation should bear fruit even still earlier, and so forth. This last assumption is now being tested on eighty varieties. In addition to all that has been said, it must be noted that only by repeating this rooting of cuttings in several vegetative generations is it fully possible to develop in the new variety of fruiters the ability to take root easily from a cutting simply planted in the bed.

O'Rourke: Effect of Juvenility on Plant Propagation (1951)
The evidence is quite clear that plants in their younger stages may express different morphological appearances in certain characters and usually root from cuttings more easily than plants in a mature or senescent condition. The progress of aging is quite closely associated with development but not necessarily with growth. The changes which take place are internal ones although there may be associated external expressions. The process is purely physiological and should not be viewed from a chronological or time age standpoint.

Sax: Juvenile characters of trees and shrubs (1958)
It has long been known that cuttings taken from young seedlings root more readily than do cuttings from the tops of mature trees. This behavior was first described by the German botanist Goebel in 1900. An extensive test made by Gardner at the University of Maryland in 1929 showed that cuttings from one-year-old seedlings of apples, pears, cherries, elms, locusts, pines and spruce rooted easily but that rooting ability declined rapidly with the age of the seedling. Cuttings from mature trees rooted with difficulty. Similar results have been found by other horticulturists.

Gol'dgauzen: Watermelon Breeding (1960)
It is noteworthy that, in crosses between C. edulis and C. colocynthis as in crosses with C. colocynthoides, the length of the vegetative period depends to a considerable degree on the respective reciprocal crosses.

Visser: Inheritance of juvenile period in apples (1965)
From the highly significant correlation between the degree of juvenility and the length of the juvenile period for either individual seedlings or for progenies as groups, it can be concluded that these parameters are genetically related.

Visser & De Vries: Precocity in apples and pears (1970)
Adult apple and pear seedlings varying in juvenile period were propagated on rootstocks. They were subsequently found to be more precocious and more productive when the juvenile period had been shorter. In view of the significant relation between vigour measured by stem diameter) and precocity of both seedlings and propagated trees, it is possible to pre-select for the potentially more precocious seedlings on the basis of vigour.

Visser, T., J. J. Verhaegh, and D. P. De Vries. A comparison of apple and pear seedlings with reference to the juvenile period, I: seedling growth and yield. Euphytica 25: 343-351. (1976)
Analysis of two incomplete half-diallel schemes of crosses, involving 22 apple and 33 pear progenies with 2500 and 5400 seedlings respectively, showed a highly significant GCA and an insignificant SCA variance for the juvenile period (J.P.). This indicates that the inheritance of the J.P. is of an additive nature, a mode of inheritance which is a function of the inheritance of a complex of factors governing 'growth'. The mean J.P. of apple progenies varied between 3.4 and 5.0 years, that of pear progenies between 4.7. and 7.0 years. The implications for breeding are discussed.

Visser, T. A comparison of apple and pear seedlings with reference to the juvenile period, II: mode of inheritance. Euphytica 16: 339-342. (1976)
Several thousand apple and pear seedlings of many progenies were studied in connection with their juvenile period (J.P.). The initially significant inverse relation between the vigour (stem diameter) and the J.P. of the seedlings became insignificant as the trees grew older, due to a retardation of growth occurring when the seedlings become generative. This relation can be used effectively in pre-selecting for vigour in the nursery. Cumulative yields were higher when the J.P. was shorter, but there was no evident link between the J.P. and annual yield in full bearing, that is to say, precocity and productivity are not directly connected. Better growing conditions and pre-selection have shortened the mean progeny J.P. of either crop by three years since the 1950's. Generally, the pear seedlings appear to grow faster, to become generative slower and to yield lower than comparable apple seedlings. The mean J.P. of apple and pear progenies averaged 4.2 and 6.0 years respectively. The difference between apple and pear may be attributable to a greater selection pressure on both precocity and productivity with apple than with pear.

De Vries: Juvenility in HT Roses (1976)
One of the main aims in rose breeding being higher flower production, selection for plants with short juvenile periods is essential, as they may produce three times more flowers in the same time span than plants with long J.P.'s. But, because highly productive plants tend to produce shorter (= less leaves and internodes) shoots, particularly the breeder of greenhouse varieties should, among the plants with short J.P.'s, select for exceptions to the rule: plants with long shoots.

De Vries & Dubois: Juvenile Period in HT Roses (1977)
Because correlations between seedling length and JP, and between production and JP are not perfect, even if high, correlation breakers do occur. It is therefore recommended to select primarily for plants with short JP's, thus ensuring productivity, and secondarily to select in this lot for the exceptions to the rule, i.e. seedlings with long shoots. Using again Ferguson's Table, it follows that in retaining the 50% of plants with short JP's, 20% of them will have an above average stem length.

Schmidt: Inheritance of the length of the juvenile period in interspecific Prunus hybrids
Abstract: A total of 3200 interspecific hybrids within and between the 2 cherry sections Eucerasus (E) and Pseudocerasus (P) were screened for their length of juvenile period.
    The E x E hybrids were the latest to flower, with P. avium and P. cerasus inheriting a longer juvenile period than P. fruticosa and P. canescens.
    The P x P hybrids start to flower one year from seed with a JP50 of 1.55 years for the group. The shortest juvenile period is inherited by P. incisa 31, P. nipponica 17, and P. concinna, the longest by P. x hillieri. The E x P and P x E hybrids show a strong maternal inheritance of the length of the juvenile period. Whereas the course of flowering in the P x E group is nearly identical with the P x P hybrids, the E x P hybrids show a slight acceleration of flowering compared with the E x E group.
     Adverse growing conditions in 1969 did not prevent P x P hybrids from flowering after 1 year, but prolonged the juvenile period in the E x E and E x P groups.