Two Radiata seedlings

[PWC]

These 2 seedlings were from the same pine cone and planted 18 months ago, as you can see there is a big difference in the size of the needles. They both appear healthy, both around 25 cms. in height with a trunk that are very similar in size. They had similar growth habits during the first 12 months but not so much over this growing season.

Is this a case of natural variation or the one with longer needles just in better condition? They have both received the same attention and are side by side on the table. I would like to think that the one with smaller needles is as healthy and will retain the smaller needle size. Should I be concerned about the lesser needle size and try to encourage more vigorous growth or continue the same treatment for both?

[Ryceman3]

From the sounds of it everything has been identical in terms of care/resources, so I would say natural variation seems like a good bet. Nothing to worry about from what I can tell, both look to be healthy and happy. Smaller needles will be your friend when they get a bit more developed so if the needles on the tree on the right stay that way you are a step ahead!
Enjoy the process!

[shibui]

Not sure how pollination works in pines - whether each seed receives separate pollen or whether one pollen grain fertilises an entire cone.
Even if the entire cone is fertilised at once, each embryo for each seed has to be fertilised which is when DNA strands split and recombine. I believe it's during that process where genes combine in relatively random order that gives us genetic variability. Sometimes it's things we can see like growth rates or colours but often the changes affect unseen attributes like hardiness, disease resistance, etc.

Interesting to note that the tree with shorter needles has also retained juvenile growth on the lower branches. Maybe it's variability is that it is slower to mature? Perhaps it will catch up in a year or 2.
It is always interesting to follow these differences through years to see where they lead.

[Raniformis]

Yeah the seedling on the right has more juvenile foliage but the mature foliage on both is about the same.

Each scale on a female cone contains 2 ovules and each seed is pollinated individually. Every single reproductive cell (both male and female) on any given tree carry exactly the same genome. Of course, pollen can travel a few hundreds miles on a windy day to keep things diverse.

I just spent the last couple of hours writing about selfies and genetics in general but lost the lot when I hit submit.

[PWC]

Not sure how pollination works in pines - whether each seed receives separate pollen or whether one pollen grain fertilises an entire cone.
Even if the entire cone is fertilised at once, each embryo for each seed has to be fertilised which is when DNA strands split and recombine. I believe it's during that process where genes combine in relatively random order that gives us genetic variability. Sometimes it's things we can see like growth rates or colours but often the changes affect unseen attributes like hardiness, disease resistance, etc.

Interesting to note that the tree with shorter needles has also retained juvenile growth on the lower branches. Maybe it's variability is that it is slower to mature? Perhaps it will catch up in a year or 2.
It is always interesting to follow these differences through years to see where they lead.

I have no experience with pine from seed(or pine in general), so next growing season should hold the answer.

I just spent the last couple of hours writing about selfies and genetics in general but lost the lot when I hit submit.

I know how frustrating that can be, thanks for taking the time to respond.

[PWC]

Did a repot on these two and realised there was a difference in my approach that I had forgotten. The one that has the smaller needles had the primary root shortened not long after germination where the other one was left alone.
Consequently the roots on the first were finer at this repot while the second had significantly heavier roots and less finer feeder roots. This may have been the cause of the disparity in the growth habits.
I have removed the heavy roots on the second, while the first had the roots spread in a radial pattern and minor root reduction. The candle extension on the second is well under way, hopefully I have not compromised it's health by removing the large roots.
The candle on the first has not pushed at all yet but does look like it soon will. Now just water and fertilise and see how they respond.

[Promethius]

I think you’ll be fine with the repotting. I have made innumerable errors with mine, but it’s basically bulletproof.

Not sure how pollination works in pines - whether each seed receives separate pollen or whether one pollen grain fertilises an entire cone.

Ooh I know this.
It’s one pollen grain per seed.
Each cone scale has a pair of ovules on its surface - each ovule needs separate pollination. The pollen grain germinates and forms a tube to deliver sperm to the ovule. So one pollen grain + one ovule —> one seed. Which happens individually for each scale on the cone.