If it is 'equal', then what are the factors that effect a cross and tilt characteristics to one or the other of the parents? If it's truly equal, then it's similar to a coin toss. Completely arbitrary on whether offspring favors one parent or the other. If there are factors aside from chloroplasts and mitochondria, then those are the ones I'd like to hear information about.
Those other effects that may cause a genetic (not environmental) reciprocal difference to appear in a characteristic:
gene imprinting or parent-of-origin expression differences
segregation distortion
transmission distortion of entire chromosomes in tetraploids
gametic selection or competition
linkage with the self-incompatibility genes
sex differences in recombination
These are effects that have been found to occur in one or more other plant species and that can result in differences in reciprocal crosses. Without specific research in daylilies we cannot know if any of these effects occur. If they do occur there is no way to predict which characteristic or characteristics might be affected nor whether the seedlings would resemble the pod parent or the pollen parent more for any specific characteristic. When they do occur in a plant species they are likely to occur only in specific crosses of certain cultivars and not in others. Without specific research we cannot predict how frequently any such effect might occur. It is unlikely that any of these effects would be generally present in a majority of daylily crosses but it is not impossible. These effects are not typically large nor extremely common in the species in which they occur.
Professional plant breeders and geneticists have been working with a knowledge of the basic (Mendelian) genetics for a little over a hundred years. Most of their work is done without making reciprocal crosses. Sometimes they make reciprocal crosses. Most of the time the reciprocal crosses do not show any differences. Sometimes they do show an effect. To place any confidence that those effects are real and not just caused by normal variability and random chance the same experiments have to be repeated by other researchers and the effects shown to be consistently present and caused by the same factor(s) consistently. Research is infrequently repeated and negative findings are often never published. Recently, with the rise of 'molecular' genetics many of the methods used by Mendelian geneticists to study inheritance have declined in use. That often makes it very difficult to interpret some modern observations.
For example, parent-of-origin expression differences:
A reciprocal cross is made, A x B producing AB seedlings and B x A producing BA seedlings. Then the researchers look at the amount of material produced by thousands of different genes in the A, B, AB and BA plants and compare those amounts statistically. Basically every measurement made on different plants will differ. So the researchers have to set a level which they will consider as indicating that a difference is 'real' and not just due to normal random variability. They will extract from their observations those genes that show differences in expression above their cut-off level and then examine whether the allele from the pod parent or the one from the pollen parent is the one that is expressed more. However, there is no information about how those differences in expression affect the visible phenotype/characteristics that we see in the plant and that would be important to breeding goals. And then the same research would need to be repeated by other researchers. Because of the complexity of the research that may or may not happen. Most such research is relatively recent and I have not followed any of it closely enough to know whether any of it has been repeated by other researchers and confirmed often enough to be accepted.
One of the catch-22s of much modern genetic research is that the characteristics being examined, such as the level of expression of different alleles, are potentially affected strongly by the environment. Environment in these cases means not only, how much water, fertilizer, sunlight, etc., the plants receive but also where they were grown, in what year they were grown, how closely they were planted together, what insects or other pests affected them, what diseases affected them, etc.
When we look at a plant we have a basic foundation for genetic effects for any characteristic that we can classify or measure. That is:
Phenotype (appearance) = Genotype + Environment + Genotype X Environment Interaction.
For some genes and some characteristics the effects of the genotype are so large and the effects of the environment and its interaction so small that they can safely be ignored. Some of the characteristics Mendel worked with are like that. But for other genes and characteristics the effects of the environment and its interaction are much more important. In those cases researchers make the environment as constant as possible so that they can ignore its effects (as well as those of its interaction). That may make the results applicable only to the conditions used in that research. Other times the researchers themselves repeat their research in different years and in different locations but usually holding all other known important environmental factors constant. This provides some information about the effects of the genotype X environment interaction.
Lets look at gametic selection or competition:
The pod parent makes the seed and its various parts while the pollen parent makes the pollen and its various parts. To do so each parent uses some of those 25,000 genes. But seed and pollen are different. So different genes (of the 25000) are used by the pod parent to make the seed and its parts than are used by the pollen parent to make the pollen. Some of the genes used to make the seed will be used by the seedling for other purposes. Some of the genes used to make the pollen will be used by the seedling for other purposes. This example is the sort of effect that can happen.
Cultivar A has a the genotype 11 for a gene that is used to make something for pollen. The gene is also used in making scapes. Cultivar B has the genotype 12 for the same gene. When cultivar A makes pollen all the pollen grains have the genotype 1. When cultivar B makes pollen half the pollen grains have the genotype 1 and half the pollen grains have the genotype 2. The gene is not used to make any part of the seed. Pollen grains with genotype 2 always beat pollen grains of genotype 1.
The cross B x A produces equal numbers of 11 and 12 seedlings because it produces only genotype 1 pollen grains.
The reciprocal cross A x B produces only 12 seedlings because genotype 2 pollen grains beat genotype 1 pollen grains.
The average scape heights of the seedlings from the reciprocal crosses will be different.
I can go through each effect in the list above and explain how it can cause differences in reciprocal crosses. But we have no information whether those effects are present in daylilies, we have no way of predicting which characteristics might be affected or in which direction the effects would change the seedlings.
The best we currently can do are the sorts of analyses I did for the characteristics and crosses recorded in the AHS cultivar registration database or in the future do our own specific well designed research to investigate characteristics we consider important in our own breeding populations. In the analysis I did for scape height and flower size I compared the relationship between the pod parent's scape height and its seedling scape height and the relationship between the pollen parent's height and its seedlings scape height. If any of those factors in the list were present (unless more than one was present and they balanced themselves out) then the seedlings should resemble one parent more than the other for scape height or flower size. That was not the case. So we can assume that none of those factors act strongly enough and generally enough in daylilies to affect scape height or flower size. But to conclude that none of those factors affect any specific cross under specific conditions in specific locations, etc. we would have to design and conduct the necessary research on the specific crosses in daylilies.
Edit #1
Maternal effects
Let's think about breeding animals for a few moments. I'll make the cross between two breeds of dogs, St. Bernards (S) and chihuahas, (C) and I will look at two characteristics, the average birth weight of puppies and the average number puppies in a litter. The data is from websites and it does not matter if it is not exactly correct. Both characteristics are different between the two breeds, with the average birth weight of St Bernards apparently one or two pounds and that of Chihuahuas is about four ounces. St Bernard litter sizes range from six to eight while those of Chihuahuas range from two to three. I make a reciprocal cross B X C and C X B and I examine their birth weights and litter sizes. There will be reciprocal differences. That is because both characteristics are mainly the mother's and not the offspring's and the father has no effect (or very little) on them. Differences in birth weight may cause differences in other characteristics in the puppies that last for years or their entire lives but would not be genetic.
Daylilies have equivalent characteristics, average seed size and the average number of seeds in each pod. Both characteristics are mainly the pod parent's and not the offspring's and the pollen parent has no effect (or very little) on them. Differences in seed weight and the nutrients stored in the seed may cause differences in other characteristics of the seedlings. Those differences may last for years but are less considerably less likely to last forever in the perennial daylily. That is because animals more or less stop growing and developing when they reach adult size. Daylilies do not stop developing, they more or less renew themselves every time they produce a new fan. Maternal effects that influenced the characteristics of the seedling's first fan or first few fans will typically decrease as each new fan is created.
Returning to genetic effects.
Basically under normal circumstances (disregarding mutations that may occur during growth) every cell in a daylily is genetically identical. Yet when one looks at a daylily there are enormous differences in appearances and functions. We see the differences - roots, crown, leaves, scape, petals, sepals, pistils, stamens, seeds, pollen, etc. yet they are all genetically identical. That is because although all cells are genetically identical not all genes have to be used by all cells.
Lets just consider seeds and pollen. Some of the genes used to produce seeds will be used only for that. Some of the genes used to produce seeds will also be used in other parts of the daylily. Some of the genes used to produce seeds will also be used to produce pollen. Some of the genes used to produce seeds will also be used to produce pollen and will also be used to produce other parts of the daylily. Some of the genes used to produce pollen will only be used for that, and so on.
Some of the genes used to produce seeds will not be used to produce pollen but will be used to produce, and in other parts of the daylily.
Some of the genes used to produce pollen will not be used to produce seeds but will be used to produce, and in other parts of the daylily.
If there is genetic variability in these two categories of genes that has visible effects in characteristics then there can be reciprocal differences.
