Seeds Need Oxygen Before Growing - Why?

[menniandscience]

hi anyone and everyone!

why do seeds need oxygen before they grow, in the time they are waiting for the right conditions to grow

thanks

 

[jim mcnamara]

Good question.
Try reading this: https://extension.psu.edu/seed-and-seedling-biology

You will see that one type of seed dormancy (seed will not germinate but is still alive) are caused by membranes that block oxygen from entering the seed.

There is a fun story about this. People in New Mexico circa 1900 discovered some funny bean seeds inside a tightly sealed Anasazi pot (~1400CE), about 500 years old. Just fooling around, they planted them. The seeds germinated and grew into a relative of the pinto beans, except the beans look really different, more like a spotted cow. Sort of like time travel for food.

Anyway they are good food, but look different. So people who want to be different cook and eat them.

What is the point? They were sealed away from oxygen for 500 years. And survived. Therefore we can say not all seeds need oxygen to remain alive.
The linked article explains the different kinds of dormancy in more of a popular science vein, so it is fun to read.

And yes, some seeds require oxygen. Not all. And they respire very slowly - meaning they are just barely burning up endosperm in the seed to stay alive, which requires some oxygen. Upper soil layers have some oxygen, as you go down the oxygen level decreases.

Anasazi:
http://historytogo.utah.gov/utah_chapters/american_indians/anasazi.html

 

[menniandscience]

thanks

why would the embryo use food if it cannot and need not to grow (while dormant)?

 

[jim mcnamara]

To maintain basic metabolic processes at an incredibly slow level. So, the embryo is still alive when exterior conditions support germination. Seeds can die in storage/dormancy all the time. For example W Atlee Burpee is one of many large, reputable seed companies. All of their seed packaging has a 'packed for XXXX' on the label, where XXXX is the year of next growing season. Many seeds become ungerminable after a time. Seeds, like pinto beans, which evolved to survive for long periods of dormancy, can take being stored for long periods in very dry conditions. Lettuce seeds (modern varieties) are an example of seeds whose germination rates decline fast with time. Pretty much regardless of storage conditions. The embryo dies for a variety of reasons.

Try this: https://pubag.nal.usda.gov/catalog/266123

 

[Ophiolite]

Seeds can die in storage/dormancy all the time. . . . .Many seeds become ungerminable after a time. Seeds, like pinto beans, which evolved to survive for long periods of dormancy, can take being stored for long periods in very dry conditions. Lettuce seeds (modern varieties) are an example of seeds whose germination rates decline fast with time. Pretty much regardless of storage conditions. The embryo dies for a variety of reasons.

Then this must mean that the seeds retained in the Svalbard Global Seed Vault and similar facilities require periodic replacment, even if such replacement occurs over decades, or centuries. In a cursory online search I didn't turn up any reference to this. Does anyone have any knowledge of how this issue is dealt with?

 

[jim mcnamara]

I cannot speak to Svalbard. The National Seed Storage Laboratory in Fort Collins, CO -
https://www.ars.usda.gov/plains-are...nt-and-animal-genetic-resources-preservation/

[personal observation]
Answer: they replace seeds stocks on a schedule. Example Hopi dryland corn was regrown for seed stock every 5 years. IIRC. The lab has a different new name since I was there long ago, and saw experimental seed/DNA storage techniques which were expected to maximize storage times for fragile/rare species DNA and seeds using near absolute zero storage. So: Two methods of coping with seed longevity. @Ygggdrasil has a good chance of having better information, since DNA storage is feasible now.
[/personal observation]

For those who do not know about Svalbard:

Svalbard is very cold, sub-freezing for most of the year.
https://www.yr.no/place/Norway/Svalbard/Longyearbyen/climate.html

The idea behind Svalbard is the Q10 factor (temperature and resulting respiration rates) should be really low, thus reducing the required replacement rates. It requires no special refrigeration. Obviously. Plus in case of war it is far from strategic areas in Europe and less likely to be damaged or irradiated.

 

[menniandscience]

"To maintain basic metabolic"
i'm not sure why would they need that. as many creatures even more complex than plant embryo can completely freeze and later when temperature is good enough the chemicals in them start moving and they back to life.

so what is and why they need to do it immediately - the basic metabolic, why can't they wait? is it for example fixing damaged cells ?

p.s

i think we need to distinguish between freezing the seeds and dormant seeds - for the other posts

 

[jim mcnamara]

I think I have explained it s it is. As to why some seeds of one species respire very slowly and other species seed does not - this is simply what was seen. I do not have a why necessarily. I do not know, I probably could guess, badly, but that is not what PF is all about.

What you are really asking is: how did species dormancy adaptations evolve.

 

[menniandscience]

no, I'm asking what is basic metabolic? using energy? for what purpose?

 

[jim mcnamara]

Alright. You do not like my answer. That's okay. Start reading - there is a reason I did not do this earlier, see if you can work out why for yourself:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC156979/
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-313X.2005.02359.x/full

I could post nearly 100 of these, but in all honesty, because different species do different things, you could make a major project out of getting through the list. And deciphering what is meant.

 

[256bits]

i'm asking what is basic metabolic

Metabolism is an encompassing word to describe the chemical reactions occurring within a cell to sustain life. The subsets are referred to as anabolism ( no oxygen required ) and catabolism ( uses oxygen ). Catabolic reactions break down complex molecules into smaller ones. You use catabolic reactions to digest your food into energy and/or heat, and you need to respire to do so. Anabolic reactions build complex molecules from smaller using energy.You use anabolic reactions to grow and make tissue and organs. ( Ever hear of anabolic steroids ).
http://www.differencebetween.net/sc...differences-between-catabolism-and-anabolism/

You need to study and get some sort of grip of the chemical processes going on in a cell during metabolism and then go on to dormancy.
Dormancy is a disruption of the normal metabolic processes through gene expression, hormones, enzymes, environment ( light, heat, water ).
Germination is the disruption of dormancy through same said factors.
The initiation and termination of dormancy and germination and what is going on in between is what the research is all about. Why do your tomatoes and apples not sprout on your kitchen counter, but potatoes and onions do? Dormancy is not just the time period from being a dry seed that you save for planting it and hoping it will grow ( those that don't may not have come out of dormancy yet and need some more time, or are actually dead due to unfavorable storage conditions ), but from some time a seed is produced on the parent plant to germination. The triggers for dormancy or germination are not as well understood as one would expect. ( except for what one hears in the general sense in the agricultural or horticultural industry and what works for them to obtain sustainability of crops and plants year after year ie when to plant and when to harvest etc, )

Rather than go through Jim's list, here is something on the subject with a table(s) ( is it complete? ) of genes and enzymes and mutants.
Complicated?
http://www.google.ca/url?sa=t&rct=j...ep1&type=pdf&usg=AOvVaw1eXcY5LQi6pQCBI1nFrogI
( Hope the link works )

 

[256bits]

I think I have explained it s it is. As to why some seeds of one species respire very slowly and other species seed does not - this is simply what was seen. I do not have a why necessarily. I do not know, I probably could guess, badly, but that is not what PF is all about.

What you are really asking is: how did species dormancy adaptations evolve.

Honestly Jim, if there was an absolute answer you would know about it., as in dormancy the chemical reactions are so very slow for study.

 

[menniandscience]

"Metabolism is an encompassing word to describe the chemical reactions occurring within a cell to sustain life. The subsets are referred to as anabolism ( no oxygen required ) and catabolism ( uses oxygen ). Catabolic reactions break down complex molecules into smaller ones. You use catabolic reactions to digest your food into energy and/or heat, and you need to respire to do so. Anabolic reactions build complex molecules from smaller using energy.You use anabolic reactions to grow and make tissue and organs. "

exactly! so why would a dormant seed need to build tissue? maybe it breath to fix the cells and inside-the-cell organs? why break molecules, why use energy etc. what do the seeds need during that time of dormant that make them use energy and have activity

 

[Ophiolite]

"Metabolism is an encompassing word to describe the chemical reactions occurring within a cell to sustain life. The subsets are referred to as anabolism ( no oxygen required ) and catabolism ( uses oxygen ). Catabolic reactions break down complex molecules into smaller ones. You use catabolic reactions to digest your food into energy and/or heat, and you need to respire to do so. Anabolic reactions build complex molecules from smaller using energy.You use anabolic reactions to grow and make tissue and organs. "

exactly! so why would a dormant seed need to build tissue? maybe it breath to fix the cells and inside-the-cell organs? why break molecules, why use energy etc. what do the seeds need during that time of dormant that make them use energy and have activity

A dormant cell is not a dead cell. It cannot and does not exist in stasis. The absence of all activity would only occur if it were dead. So some activity must necessarily be present.