The outer pollen wall, or exine, is more structurally complex than any other plant cell wall, comprising several distinct layers, each with its own organizational pattern. Since elucidation of the basic events of pollen wall ontogeny using electron microscopy in the 1970s, knowledge of their developmental genetics has increased enormously. However, self-assembly processes that are not under direct genetic control also play an important role in pollen wall patterning. This review integrates ultrastructural and developmental findings with recent models for self-assembly in an attempt to understand the origins of the morphological complexity and diversity that underpin the science of palynology.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2007.02060.x

Pollen wall development in flowering plants

The first haploid angiosperm, a dwarf form of cotton with half the normal chromosome complement, was discovered in 1920, and in the ninety years since then such plants have been identified in many other species. They can occur either spontaneously or can be induced by modified pollination methods in vivo, or by in vitro culture of immature male or female gametophytes. Haploids represent an immediate, one-stage route to homozygous diploids and thence to F(1) hybrid production. The commercial exploitation of heterosis in such F(1) hybrids leads to the development of hybrid seed companies and subsequently to the GM revolution in agriculture. This review describes the range of techniques available for the isolation or induction of haploids and discusses their value in a range of areas, from fundamental research on mutant isolation and transformation, through to applied aspects of quantitative genetics and plant breeding. It will also focus on how molecular methods have been used recently to explore some of the underlying aspects of this fascinating developmental phenomenon.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-7652.2009.00498.x

Haploids in flowering plants: origins and exploitation.

The Cell in Development and Heredity

Haploids are interesting components of the range of genetically aberrant types that are found when cytogenetic investigations are made into many angiosperm species. As a consequence of their unique constitution, they offer new possibilities for the investigations of many cytological and genetical problems. They also present a new range of problems intrinsic to their own chromosomal status.

Haploid Angiosperms

CHAPTER NINE – Sexuality of Angiosperms

Pollen Formation in Oenothera gigas

A Cytological Study of Pollen Development in Lactuca

I~ 1929, a single plant survived to matuzity in a culturc of nonviable _F 1 hybrids resulting from Oe. rubricalyx pollinated by Oe. eriensis. It was dwarfed in the size of all ira parts, as well as completely sterile, and was finally suspected of being a haploid mutant. Subsequent cytological examination has ahown this to be the case. A short note has already been published on the subjeet (Gates, 1929). Having observed this haptoid, the senior author believes that certain amall aberrant plants, not of the usual dwarf types, which have occasionaUy occurred in bis cultures in earlier years, were also haploid in nature. Ir is desirable that geneticists should keep in mind the possibility of the occurrence of such haploid sterile small plants in their cultures, for they ate probably of more frequent occurrence than has hitherto been supposed. The sterility of such planta is in some cases more conspicuous than their smallness of size.

A new haploidOenothera, with some considerations on haploidy in plants and animals

"Natural selection or the preservation of favoured races in the struggle for life" is an explanation primarily of adaptation and only secondarily of the origin of species. It rests on the assumption that the differences between individual members of a species which live together in the same district are heritable, and that they may determine the life or death of the individuals in question at an earlier or later time than one another. In other words, that definite variation in structure or in function may be responsible for a selective death-rate. It is evident that this selective death-rate will only be recognizable statistically, and that a heavy non-selective infantile death-rate, such as that which occurs generally in marine teleosts, merely reduces the population within which selection of adults may operate. The existence of such a selective mortality is fundamental to the theory, and various authors, from the time of Weldon, have tried to establish its occurrence in definite cases, always without any significant result. It is presumably true that relatively gross abnormalities lead to early death, but in some cases (e.g., Rhynchonella) the average size of asymmetrical shells seems, on a mere inspection, to be no smaller than that of normal individuals from the same horizon and locality. It would thus be valuable to have any new evidence on this point, or indeed any suggestion of cases which might be capable of investigation. The nature of the variations which do occur in nature and which may provide the raw material of evolution, requires experimental investigation. The varieties recognized by systematists, are, I think rightly, held by them to include two types: those which occur within a single population, and which therefore cannot be accounted for by environmental effects (except for those special cases involving microclimates), and those which are assumed to be related to local variations in the environment, and are hence of a geographical significance. * In some special cases, e.g., the spring and summer broods of moths, the varieties are clearly the result of climatic changes, but in most, e.g.,

https://www.jstor.org/stable/pdfplus/82031.pdf

R. Ruggles Gates

Papers

Pollen Formation in Oenothera gigas

A Cytological Study of Pollen Development in Lactuca

A new haploidOenothera, with some considerations on haploidy in plants and animals

A Discussion on the Present State of the Theory of Natural Selection

The Trisomic Mutations of Oenothera