Hello,

Not really my field, but I read some time ago that seed size variability could be a strategy to handle unpredictable environments.

The title of the article is below, it should contain references to the subject.

Article Crean AJ, Marshall DJ.. Coping with environmental uncertaint...

also it depended on site of seed on plants( that is called site effect) and time of filling the seed that is various. Usually the seed with big size can emergence  in  deeper hole and small seeds can germinate faster. Often, multisize and shape can be seen in wild varieties

Thank you. In the mean time I found numerous papers dealing with that problem. As far as I can see this is largerly unasnwered question. For some species this is unpredictible environment, for some different part of plant that are resource-limited, for some amount of pollen that they will recive. This is really interesting!

Hi,

Two types of factors are involved when explaining the difference in seed size in same plant. 1) External factor- It roughly includes the season of seed production, abundance of pollinators if the sp. needs pollinating agents, distance from the pollen source etc. 2) Internal factors- It includes age of the mother plant, whether any sort of self-incompatibility reaction is involved during fertilisation, position of the sink/ seed in the mother plant, random supply of food from source to sink and ultimately the evolutionary adaptation to perpetuate. The range of size in same seed lot provides wide range of dormancy hence helps seed to germinate periodically to find a favorable window when germinated seedlings can grow uninterruptedly. The vigour level of seed is also proportionate to its size, it means the seed lot would have different potential to withstand harsh environment so that at least few seeds can multiply and advance to next generation. Another observation is that when plants encounter harsh situation, it produces lots of smaller seeds as the smaller  seeds germinate first before larger seeds. Also it has been observed when same plant in same flash produces seeds of different size, the proportion of larger seeds is less as compared to smaller seeds. It implies that resource-limited individual tries to produce more small seeds in compliance with rules of energy-economy, same time it produces some large seeds so that the risk of non-perpetuation is minimised. 

I am agree with the answer of  A.Maity

good question. it depends on several factors such as: pluviothermic conditions corresponding to the maturity of seeds ,  seeds formation period, phenological stage and the timing of flowering during the  plant life cycle  and then especially the position of the fruit on the plant. Example: For tomatoes, the first fruits are formed on the individual big size ,  those formed at the end of the cycle and at the end of the individual are small.

Try

ELWELL et al  2011 Separating parental environment from seed size effects on

next generation growth and development in Arabidopsis Plant, Cell and Environment (2011) 34, 291–301 doi: 10.1111/j.1365-3040.2010.02243.x

And

Boyd et al Int. J. Plant Sci. 168(2):205–214. 2007.

1058-5893/2007/16802-0007$15.00

It depends on resource allocation, with seeds later in the season decreasing in size because of lower resources. See my project on fruit size selection at my profile.

Thanks!

Andrew :-)

-On the other hand, the position of the flower on the plant has an effect. For example, the flowers of the base, generally have a larger seeds than those of the upper part of the individual.

There are strong trade-offs at play that can generate seed size variation in plants dispersed by granivores such as waterfowl. Larger seeds will have benefits in local competition, whereas smaller seeds have a better chance of long-distance dispersal owing to higher survival of gut passage (and possibly longer maximum retention times). Here's a review of relevant literature

https://www.researchgate.net/publication/306038948_Dispersal_of_plants_by_waterbirds

Chapter Dispersal of plants by waterbirds

Please check it.

https://www.frontiersin.org/articles/10.3389/fevo.2021.698885/full

Fruit and seed size are different issues. Increasing seed size will normally increase resources for the young plant, while increasing fruit size will will - at least in animal-dispersed species - increase resources for the frugivore without necessarily changing seed sizes. In Michal's acorn example, fruit and seed size are tightly correlated and the reward for the dispersal agent is the same as the resources for the seedling, but this is not usually true. Presumably it is not possible for a plant to produce seeds of identical size, for reasons mentioned in previous answers, but it is reasonable to ask if there is evidence of stabilizing selection favoring the mean size.

this type of observation exists especially in the case of populations it is a kind of adaptation of the plant with the presence of genes which are expressed in this form then in cultivars it is less

Seed size of same plant can vary because of different factors. For example, the position of the seed from seeds, position of fruits where we get the seeds from, the position to the light, space, etc. can affect he size of seeds.

also in trees the size of fruit depends on the situation of the fruit in relation to the trunk and the number of leaves moreover if the fruit and individual is larger in relation to the two or more it is a question of availability of the sap

Many reasons for a disparity between seed size and plant size have been suggested, and many aspects of plant development are thought to be related to seed size. Larger seeds are better able to support themselves initially, while smaller seeds have a better chance for dispersal over a wide area, helping at least some seedlings survive.

It's due to a natural phenomenon called polymorphism leading to seed size heterogeneity.

It's two types.. position on the Fruits and within fruits.

It's due to a natural phenomenon called polymorphism leading to seed size heterogeneity.

It's two types.. position on the Fruits and within fruits.

When a seed is formed by a plant, it is the result of pollen fertilizing an egg (ovule). Whether the resulting seed “comes true,” that is, produces plants identical to the plant that it was harvested from, depends on whether it is outcrossed, inbred, or hybrid. These three options determine whether the two sets of genes (one from the pollen and one from the ovule) are likely to be identical or very different.

INBRED

In inbred plants, the eggs are fertilized with pollen from the same plant. (Another term for this that you may have heard is self-pollination). The progeny will each have two identical (or nearly so) sets of genes, exact copies of their parents, and very similar to each other. Most peas and beans are inbred. Since seed from self-pollinated plants will produce plants very like the plant it was produced on, these kinds of plants are ideal for seed saving.

OUTCROSSED

Outcrossed plants require pollen from a different plant to fertilize the egg (also called cross-pollination). Some outcrossing species have the female and male parts in separate flowers (corn or squash) or even separate plants (asparagus). Others have both parts in the same flower, but the egg will accept pollen only from another flower or plant. Apples are an example of this – that is why a separate pollinator tree is needed to obtain fruit. The two sets of genes in the offspring of outcrossed plants tend to have a lot of variation, so that the outcome of crossing is less predictable, somewhat like the variation between siblings in a human family. Seed from outcrossed plants will not necessarily come true; thus you should not save seed from these plants if you want to be certain that the plants will be exactly the same as their parents. However, if you have grown only one variety (and your neighbors have grown the same variety or are far enough away to avoid wind- or insect- cross pollination), you can still expect fairly consistent results from that seed.

HYBRIDS

Hybrids result from crossing two different inbred lines. All of the first generation of plants from this cross will contain the exact same two sets of genes (one from each line) and thus will be identical to each other. This first generation is what you buy in a seed packet marked “Hybrid” or “F1”. However, the next generation (the plants that will grow from seed produced from plants grown from “F1” seed) will contain a random mixture of genes, resulting in plants that may have a whole range of desirable and undesirable characteristics. Thus you should not save seed from F1 or hybrid plants if you want to be certain that the plants grown from that seed will be the same as their parents.

Plant Types

How can you tell whether a plant is outcrossed, inbred, or hybrid? First of all, look for the words “hybrid” or “F1” on seed packets. Any plant that has separate male and female flowers is most likely outbred. Plants with closed flowers, such as peas and beans, are usually inbred. Sometimes it will not be obvious whether the plant is inbred or outbred. Following is a list of plants that either mostly outcrossed or inbred.

It could be interpreted as a kind of bet-heging strategy. You may want to have a look to the book by C. Herrera "Multiplicity in unity"

Because i’t function of the position seeds on the plant.

Because i’t function of the position seeds on the plant.

Because i’t function of the position seeds on the plant.

Because i’t function of the position seeds on the plant.