Constitution and Crossing

Two species that are adapted to different environmental conditions can be said to possess different constitutions. That is, one may be constitutionally suited to live in a bog, while the other’s constitution allows it to survive on dry land. In some cases, the constitution of an individual may be altered by raising it from the seed in a different habitat. For instance, Burbank seemed to have had fewer problems with crinums than Herbert did. Perhaps the reason was that Herbert hired men to collect mature specimens from the wild, whereas Burbank generally raised his plants from seed.

I think it would be worth the experiment to plant seeds of Crinum longifolium (Herbert’s C. capense) together with seeds of C. zeylanicum or C. scabrum. Then, when the plants flower, cross them to learn whether the constitutions of the species have become similar enough to allow them to produce fertile offspring.

Kains: Daniel's Experiments and Conclusions (1916)
Analogy in habitat seems to be a more or less important factor. Thus Phlox decussata, which grows in humid soils, has not been successfully grafted by Daniel on P. subulata, which grows on dry soils; though parsley, which prefers a dry soil, succeeds when grafted with Sison ammonium, which prefers humid soil. In the case of trees, pears are grafted on quinces in rich soil and on pear seedlings in poor soil, etc. Different soils, then, are not the most serious obstacles to success in grafting, but they seem to have more or less marked influence on the duration of the graft.

Burbank: Crinums. (1914)
My object was to combine the good qualities of the tropical and subtropical species with those of the hardy ones that had become acclimated in California. No difficulty was experienced in crossing the various species, and hybridization was carried out in the usual way, different pairs of species being mated and then the hybrid forms in subsequent seasons remated, noting of course at all stages which combinations seemed to produce the best results. Mixed hybrids were finally produced that combined the strains of many species.

Herbert: Amaryllidaceae. P. 341 (1837)
It was my opinion that fertility depended much upon circumstances of climate, soil and situation, and that there did not exist any decided line of absolute sterility in hybrid vegetables, though from reasons which I did not pretend to be able to develop, but undoubtedly depending upon certain affinities either of structure or constitution, there was a greater disposition to fertility in some than in others. Subsequent experiments have confirmed this view to such a degree as to make it almost certain—that the fertility of the hybrid or mixed offspring depends more upon the constitutional than the closer botanical affinities of the parents. The most striking and unanswerable proof of this fact was afforded by the genus Crinum, which is spread round the whole belt of the globe, within the tropics and within a certain distance from them, under a great variety of circumstances affecting the constitution of individuals, which nevertheless readily intermix, when brought together by human agency. The plant called Crinum Capense (formerly Amaryllis longifolia), impregnated by either Crinum Zeylanicum or scabrum, both at that time also called Amaryllis, produced offspring, which during sixteen years proved sterile, probably because, notwithstanding their botanical affinity, the first is an extra-tropical aquatic plant, and the two latter tropical plants which affect drier habitations and readily rot, at least in this climate, in a wet situation. The same C. Capense, impregnated by Crinum pedunculatum, canaliculatum, or defixum, produces a fertile cross, though they are so dissimilar as to have been placed in different genera, and the author was formerly reproached by botanists as having committed an absurdity when he insisted upon uniting them. The reason of the fertility of their joint produce seems to be, that they area all aquatic or swamp plants; and it may be further observed that the crosses with the two former, the plants being all extra-tropical, are much more fertile than that between C. Capense and defixum, because the latter is a tropical plant. The mules between Scabrum and Capense having continued so many years with every appearance of absolute sterility, without any change of situation or treatment, at last produced one good seed in 1834 and another in 1835. These facts were of such an overbearing nature, that it became impossible for those, who had charged the author with absurdity for uniting the parents under the genus Crinum (to which even certain other plants were then asserted to be more nearly allied than the species at that time called Amaryllis), to contend any longer that they, producing a fertile offspring, were of different genera, and they will probably be never again disunited in any botanical work; but the facts furnish much ground for the serious consideration of men of science. It happens (as if expressly designed to overthrow the theory, that the identity of species is proved by fertility or sterility in the mixed issue), that, while C. Capense, Zeylanicum, and scabrum, are very similar in their general appearance, and yield an offspring which has been found quite sterile except in the case of the two seeds above mentioned, C. Capense and pedunculatum are as unlike as perhaps any two species of any known genus; and if it were asserted that C. Capense and pedunculatum are one species, and C. Capense and scabrum two species, the assertion would appear, to any person looking at the plants, too preposterous to require a serious answer.

In further confirmation of the fact that the sterility depends on constitutional discrepancy, or difference of what medical men call idiosyncrasy, may be adduced the curious plant figured in the Botanical Magazine under the name of Crinum submersum, which was found by my collector in a pond or flooded spot not far from Rio Janeiro, in company with a small variety of C. erubescens, and appeared to be exactly intermediate between that aquatic plant and C. scabrum, which grows on high ground amongst the woods. It is absolutely sterile, the anthers being always shrivelled and the pollen dry, and it is not materially different from the mules raised in our stoves between C. scabrum and a larger variety of C. erubescens, the latter being of course a finer mule, but with exactly the same barrenness of the anthers. C. submersum is certainly a natural cross, in consequence of the pollen of C. scabrum having been brought to the lake by some humming-bird or insect which touched the stigma of the aquatic species. The same sterility has been found in C. amabile and C. angustum, which are undoubtedly mules accidentally produced between dry-land and swamp-species, the former probably between Zeylanicum and procerum, the latter between C. Zeylanicum and bracteatum; as also C. longiflorum (Amaryllis longiflora of the Botanical Register), which is an accidental cross between C. Capense and erubescens, one variety of it having been produced at Demerara, the other in Jamaica. The fact being established with respect to one genus, that the species which have most botanical affinity and general likeness, if they delight in a different state of soil or of atmosphere, produce a barren cross, while the most dissimilar, if they possess the same constitutional predilections, give birth to a fertile plant, cannot remain as an isolated circumstance, but must be considered by every unprejudiced and philosophical mind with reference to the whole vegetable creation.

Henslow: Hybridisation and its Failures (1900)
CONSTITUTIONAL AFFINITY AND STERILITY.—Admitting the fact that the closer agreement there may be between the forms of two species, the more likely is it that they will cross, yet it is not universally true; so that, leaving "morphological affinity" out of the question, we have to depend on, for want of a better expression, what one may call "constitutional affinity," cautioning the reader that this is a phrase which covers our profound ignorance of the true nature of physiological affinity!

Micuhrin: Selected Writings p. 192-193 (1949)

In 1900 I fertilized the flowers of the apple Malus Niedzwetzkyana—a pure species—with the pollen of Antonovka. The former is remarkable for its marked red colouring of both leaves and fruit. As a result, one fruit set and ripened, from it I obtained fourteen seeds, and in due course the following types of seedlings: six with red leaves and seven with green leaves, and one had one side of its shoots and leaves coloured red and the other green. Both the red and the green seedlings developed with the usual vigour, whereas the striped one (evidently due to the difference in the structure of its cells on both sides) at first grew very sparingly—was about half the size of the rest, but gradually the red colouring expanded, and when it finally encircled the circumference of the trunk, the growth of the sapling increased and the tree reached the height of the others. Finally, in 1914/15 all the trees bore fruit; it so happened that the seven red trees produced fruit of about the same size, but twice as large as those of the mother plant, all of the winter type and of approximately the same flavour. The seven green forms produced fruit that greatly varied in size, shape, colouring (for the most part pale and designed) and flavour—from very sweet to extremely sour, a property not met with either in the paternal plant—Antonovka, or in the mother—the Niedzwetzkyana apple. Such a diversity of types was evidently the result of the manifestation of the recessive characters of Antonovka's distant kin. Furthermore, from the self-pollination of the seven red hybrids due to the dominance of the Niedzwetzkyana pure-species type trees were obtained the fruit of which had an extremely red flesh. On the other hand, if the flowers of the red hybrids were pollinated by any green hybrid or by any other cultivated variety, the trees produced from the cross yielded fruit that were coloured only from the outside, whereas the flesh remained white and was of a miserable flavour.

When the pollen of the first red hybrids was used to fertilize the different cultivated varieties the resulting hybrids yielded fruit of completely red colour but only of the rind; their flavour was excellent and always of the winter type. The latter property was the result of the shorter period of vegetation in our parts as compared with the longer period necessary for the Niedzwetzkyana apple. The seedlings of the first seven green hybrids when self-pollinated, yielded in the second generation only typical wildings; the same occurred when they were crossed with cultivated varieties. Here it is evident that the recessive characters of Antonovka's wild ancestors proved to be dominant. Now just how is one to apply Mendel's laws in such a case? 

In the cited instance if we consider the increased size and better flavour of the fruit from the first-generation red hybrids as the result of the influence of the Antonovka characters, then where does the diversity of types obtained from the green hybrids come from? Particularly, since they failed to manifest a single character of their parent plants. Furthermore, why does the pollen of the red hybrids when used to fertilize other old cultivated varieties, despite its dominance, produce fruit of good quality, whereas the pollen of the first seven green hybrids produces only wildings? Even if segregation does take place, in this case, at any rate, half of the characters belong to Antonovka's very distant past and not to the direct and immediate parents of the hybrids.

One point is clear, namely, that the characters of the Niedzwetzkyana apple, being those of a pure species, in all cases prove to be strongly dominant and suppress and leave in a recessive state most of the characters of other varieties. The cited case likewise demonstrates one of the reasons for dwarfed growth, proving it to be due to the correlative influence of the incongruity of structure and growth of the cells in the different halves of the plant; externally no other characters were manifest except the red colour of the bark.

CybeRose note: If Michurin had mentioned only the six red and seven green seedlings, I might have guessed that the Niedzwetzkyana is heterozygous for something, possibly an inversion. But the striped seedling that languished until the red coloring encircled the stem does suggest a constitutional conflict.

Lysenko: Agrobiology 440-441 (1954)
On crossing Hostianum 0237, a winter wheat, with spring wheat 1160 and 1163 (the latter two wheats being full sisters), the seeds obtained were normal. At first sprouts normal in their external appearance developed from them. But when the third leaf appeared the first shrivelled up. As soon as the fourth appeared the second shrivelled up. All the time only the last two leaves remained alive on the plant. In the end the plant perished. Thousands of such plants were under experiment at one time or another and not one of them lived long enough to ear; all died. The Mendelist-Morganists would attribute such a phenomenon to the action of lethal genes. But they would have nothing to offer wherewith to combat this action. They would declare it fatal, irresistible, and would endeavour to show that in such cases there is only one solution: don't take for crossbreeding plant or animal organisms that have lethal genes. Yet a cross of the same combination, Hostianum 0237 and 1160, produced hybrids which vegetated splendidly in these very same greenhouses and yielded viable, nonperishable plants. The point is that one of the components (paternal form 1160) is a spring variety, but for two generations before crossing it was sown in Odessa, not in spring but in the autumn. Then a cross was effected. This proved sufficient to obtain viable offspring. A different rearing of wheat 1160 altered the plant's sex cells; hence the difference in the result of hybridization.

CybeRose note: I'm reminded of a couple of vaguely related items: "... in a spectacular series of experiments in 1950s, Dr. Janet Harker showed that cockroaches containing two pacemakers entrained several hours out of phase with each other (e.g., NYC time in the left lobe and New Zealand time in the right lobe) developed intestinal cancer—something rarely seen in insects." Serotonin, Melatonin, Immunity and Cancer

The other was a report that Lycoris seedlings maintained at constant temperature and photoperiod will continue growing for two years. But that a change in heat or light will trigger a seasonal dormancy that repeats every year regardless of temperature and photoperiod.

Konstantinova: Michurin methods, alfalfa (1960)
It has been found that when wild forms are placed in unaccustomed environments the type of their development is changed and the hereditary capacity weakened even within one generation. For example, when grown under free pollination conditions with common lucerne the progeny of two-year plants of wild Angarian lucerne produced up to 20% pronounced hybrid plants, the progeny of the three-year plants up to 58% and of the four-year plants up to 89%.

When hybrids are sterile or only weakly fertile, we may be inclined to give up and try something easier. But on occasion a closer look will reveal that the hybrids are fertile only within a very narrow range of conditions. Lyubimova (1960), for example, found that a wheat-Agropyron hybrid was much more fertile at 20°C than at 35 to 37°C.

Stout: Cyclic manifestation of sterility in Brassica pekinensis and B. chinensis (1922)
It is to be noted that the complete life cycle of flowering plants involves two periods of vegetative vigor and maturity; one for the sporophyte and one for the gametophyte. The former culminates in the production of spores and the latter in the production of gametes. The generations are antithetic. In its length of life, vigor of vegetative growth, and reproductive power (number of gametes), the gametophytic phase has become relatively weak and highly specialized. In the sporophyte great vegetative vigor is correlated with great reproductive vigor in the production of spores (which are, however, in themselves asexual) and in the nurture of the gametophyte and the embryo. Sex differentiation in the great group of flowering plants has been pushed back during the progress of evolution into the sporophytic stage of the entire cycle, and here sexuality now culminates in seed formation in which the nutrition of the embryo is a most important factor. Sexual reproduction in these higher plants has become more and more inter-related with the vegetative phase of the sporophyte and subject to its internal and biogenetic regulation.