Gemeni AI

[growsinse79]

I asked Gemini why all ppfd isn't created equal and this is the answer.




Photosynthetic Photon Flux Density (PPFD) is a critical metric for measuring light in horticulture, but the raw number alone doesn't tell the whole story. The phrase "not all PPFD is created equal" highlights that several factors influence how effectively a given PPFD value translates into plant growth. Here's a summary of why that's the case:

1. The Light Spectrum Matters​

PPFD measures the quantity of photons within the Photosynthetically Active Radiation (PAR) range (400-700 nm), but it doesn't account for the quality of that light. Plants respond differently to specific wavelengths:

• Blue Light (400-500 nm): Crucial for vegetative growth, promoting compact plant structure, thicker leaves, and robust stems.
• Red Light (600-700 nm): Highly effective for photosynthesis and essential for flowering and fruiting.
• Green Light (500-600 nm): While historically considered less important, green light can penetrate deeper into the plant canopy, reaching lower leaves that would otherwise be shaded and contributing to overall photosynthesis.
• UV and Far-Red Light (outside the traditional PAR range): These can also influence plant development, affecting things like flowering, stem elongation, and the production of beneficial compounds.

A light source with a high PPFD value but a poor spectrum (e.g., one that's exclusively green) will be far less effective for plant growth than a light with a lower PPFD but a balanced, "full-spectrum" output.

2. Light Intensity and Plant Efficiency​

Plants have a "light saturation point," a maximum amount of light they can use for photosynthesis. Past this point, providing more intense light (a higher PPFD) doesn't increase photosynthesis and can even become detrimental. Excess light energy is converted into heat, which can stress the plant, causing leaf burn, bleaching, and reduced growth.
Furthermore, plants use light less efficiently as PPFD increases. A plant might grow faster with a lower PPFD over a longer period than with a very high PPFD over a short period, even if the total amount of light received is the same. This brings us to the next point:

3. The Importance of Daily Light Integral (DLI)​

PPFD is an instantaneous measurement of light intensity at a specific location, while Daily Light Integral (DLI) is a cumulative measurement of the total amount of light a plant receives over a 24-hour period. DLI is often a more reliable indicator of overall plant health and growth because it accounts for both light intensity (PPFD) and the duration of the light cycle. A plant with a low PPFD but a long light cycle can have the same DLI as a plant with a high PPFD but a short light cycle. For many species, the former approach can lead to more efficient growth and healthier plants.

4. Plant Species and Growth Stage​

Different plants have different light requirements, and these needs change throughout their lifecycle. A PPFD that is ideal for one plant species might be too high or too low for another. For example:

• Seedlings: Require lower PPFD (e.g., 100-300 μmol/m²/s) to prevent damage to their delicate leaves.
• Vegetative Stage: Require a moderate PPFD (e.g., 400-600 μmol/m²/s) for robust leaf and stem growth.
• Flowering/Fruiting Stage: Often require the highest PPFD (e.g., 600-1000 μmol/m²/s) to support the energy-intensive process of producing flowers and fruits.

5. Distribution and Uniformity​

A single PPFD measurement taken directly under a grow light might be very high, but the intensity can drop off significantly just a few inches away. A non-uniform distribution means that different parts of the plant canopy are receiving unequal amounts of light. This can lead to uneven growth, with some parts of the plant thriving while others are stunted. The "average canopy PPFD" and the uniformity of the light are just as important as the peak PPFD value.

 

[growsinse79]

Q.) Why does back crossing make weaker plants?

Backcrossing, the process of repeatedly crossing a hybrid with one of its parents, is a common and powerful technique in plant breeding.1 Its purpose is typically to introduce a specific, desirable trait (like disease resistance) from a "donor" parent into an "elite" or "recurrent" parent while recovering the desirable genetic background of the elite parent.2



However, repeated backcrossing can lead to a phenomenon known as "inbreeding depression," which can result in weaker offspring. Here's why this happens:

• Inbreeding and Homozygosity: Backcrossing is a form of inbreeding. Each time a plant is backcrossed to a single, genetically uniform parent, the offspring become more genetically similar to that parent. This process increases the level of homozygosity, where an individual has two identical copies of a gene at a particular location on a chromosome.
• Masking Deleterious Recessive Alleles: Most plants and animals carry a number of recessive genes that are harmful or "deleterious." In a diverse, outcrossing population, these genes are usually masked because they are paired with a dominant, healthy allele. The individual is a heterozygote and doesn't express the harmful trait.
• Unmasking Deleterious Alleles: As backcrossing increases homozygosity, there's a higher chance that two copies of the same deleterious recessive allele will be paired together. When this happens, the harmful trait is expressed, leading to reduced vigor, smaller size, lower fertility, and other undesirable characteristics. This is a key mechanism of inbreeding depression.
• Loss of Heterosis (Hybrid Vigor): The opposite of inbreeding depression is heterosis or "hybrid vigor," where the first-generation offspring of two genetically different parents are often stronger, larger, and more productive than either parent. This is due to a high degree of heterozygosity, which masks deleterious recessive alleles and can also be attributed to other complex genetic interactions. Backcrossing essentially reverses this process, reducing heterozygosity and causing the loss of hybrid vigor.

It's important to note that backcrossing is a controlled and deliberate process used by breeders to achieve a specific goal.3 By carefully selecting for the desired trait in each generation and continuing the backcrossing process, they aim to recover the elite parent's genetic makeup as much as possible while incorporating only the new gene of interest. However, even with careful selection, the increased homozygosity can still lead to a decrease in overall plant health and vigor.4

 

[steamroller]

Q.) Why does back crossing make weaker plants?

Backcrossing, the process of repeatedly crossing a hybrid with one of its parents, is a common and powerful technique in plant breeding.1 Its purpose is typically to introduce a specific, desirable trait (like disease resistance) from a "donor" parent into an "elite" or "recurrent" parent while recovering the desirable genetic background of the elite parent.2



However, repeated backcrossing can lead to a phenomenon known as "inbreeding depression," which can result in weaker offspring. Here's why this happens:

• Inbreeding and Homozygosity: Backcrossing is a form of inbreeding. Each time a plant is backcrossed to a single, genetically uniform parent, the offspring become more genetically similar to that parent. This process increases the level of homozygosity, where an individual has two identical copies of a gene at a particular location on a chromosome.
• Masking Deleterious Recessive Alleles: Most plants and animals carry a number of recessive genes that are harmful or "deleterious." In a diverse, outcrossing population, these genes are usually masked because they are paired with a dominant, healthy allele. The individual is a heterozygote and doesn't express the harmful trait.
• Unmasking Deleterious Alleles: As backcrossing increases homozygosity, there's a higher chance that two copies of the same deleterious recessive allele will be paired together. When this happens, the harmful trait is expressed, leading to reduced vigor, smaller size, lower fertility, and other undesirable characteristics. This is a key mechanism of inbreeding depression.
• Loss of Heterosis (Hybrid Vigor): The opposite of inbreeding depression is heterosis or "hybrid vigor," where the first-generation offspring of two genetically different parents are often stronger, larger, and more productive than either parent. This is due to a high degree of heterozygosity, which masks deleterious recessive alleles and can also be attributed to other complex genetic interactions. Backcrossing essentially reverses this process, reducing heterozygosity and causing the loss of hybrid vigor.

It's important to note that backcrossing is a controlled and deliberate process used by breeders to achieve a specific goal.3 By carefully selecting for the desired trait in each generation and continuing the backcrossing process, they aim to recover the elite parent's genetic makeup as much as possible while incorporating only the new gene of interest. However, even with careful selection, the increased homozygosity can still lead to a decrease in overall plant health and vigor.4

Punnett Square; I needed to basically understand this to breed and create fish strains.
I won't say I get it completely but what is known by those who practice is that new blood is needed every so often.
Even if new blood is square one and you are on f4 it needs to be introduced to add strength/virility.
The line between in-breeding and line breeding is very thin and blurred. Locking in a strain is not as quick or easy as many think if you want long term success.

Punnett Square in Genetics

Learn about the Punnett square in genetics. Get example, definitions of key terms, and discover the uses and limitations of the squares.

sciencenotes.org

 

[Bandit420]

I asked Gemini why all ppfd isn't created equal and this is the answer.




Photosynthetic Photon Flux Density (PPFD) is a critical metric for measuring light in horticulture, but the raw number alone doesn't tell the whole story. The phrase "not all PPFD is created equal" highlights that several factors influence how effectively a given PPFD value translates into plant growth. Here's a summary of why that's the case:

1. The Light Spectrum Matters​

PPFD measures the quantity of photons within the Photosynthetically Active Radiation (PAR) range (400-700 nm), but it doesn't account for the quality of that light. Plants respond differently to specific wavelengths:

• Blue Light (400-500 nm): Crucial for vegetative growth, promoting compact plant structure, thicker leaves, and robust stems.
• Red Light (600-700 nm): Highly effective for photosynthesis and essential for flowering and fruiting.
• Green Light (500-600 nm): While historically considered less important, green light can penetrate deeper into the plant canopy, reaching lower leaves that would otherwise be shaded and contributing to overall photosynthesis.
• UV and Far-Red Light (outside the traditional PAR range): These can also influence plant development, affecting things like flowering, stem elongation, and the production of beneficial compounds.

A light source with a high PPFD value but a poor spectrum (e.g., one that's exclusively green) will be far less effective for plant growth than a light with a lower PPFD but a balanced, "full-spectrum" output.

2. Light Intensity and Plant Efficiency​

Plants have a "light saturation point," a maximum amount of light they can use for photosynthesis. Past this point, providing more intense light (a higher PPFD) doesn't increase photosynthesis and can even become detrimental. Excess light energy is converted into heat, which can stress the plant, causing leaf burn, bleaching, and reduced growth.
Furthermore, plants use light less efficiently as PPFD increases. A plant might grow faster with a lower PPFD over a longer period than with a very high PPFD over a short period, even if the total amount of light received is the same. This brings us to the next point:

3. The Importance of Daily Light Integral (DLI)​

PPFD is an instantaneous measurement of light intensity at a specific location, while Daily Light Integral (DLI) is a cumulative measurement of the total amount of light a plant receives over a 24-hour period. DLI is often a more reliable indicator of overall plant health and growth because it accounts for both light intensity (PPFD) and the duration of the light cycle. A plant with a low PPFD but a long light cycle can have the same DLI as a plant with a high PPFD but a short light cycle. For many species, the former approach can lead to more efficient growth and healthier plants.

4. Plant Species and Growth Stage​

Different plants have different light requirements, and these needs change throughout their lifecycle. A PPFD that is ideal for one plant species might be too high or too low for another. For example:

• Seedlings: Require lower PPFD (e.g., 100-300 μmol/m²/s) to prevent damage to their delicate leaves.
• Vegetative Stage: Require a moderate PPFD (e.g., 400-600 μmol/m²/s) for robust leaf and stem growth.
• Flowering/Fruiting Stage: Often require the highest PPFD (e.g., 600-1000 μmol/m²/s) to support the energy-intensive process of producing flowers and fruits.

5. Distribution and Uniformity​

A single PPFD measurement taken directly under a grow light might be very high, but the intensity can drop off significantly just a few inches away. A non-uniform distribution means that different parts of the plant canopy are receiving unequal amounts of light. This can lead to uneven growth, with some parts of the plant thriving while others are stunted. The "average canopy PPFD" and the uniformity of the light are just as important as the peak PPFD value.

This is one of those things that I've always felt reading plants is really the best meter to have around because that, other than a spectrometer built into the meter, can give a full picture. A PPFD of 2000 is great on the surface but what if the 2000 is from orange or green? Yeah, worthless grow light there.
Many times in the past LED companies have thrown out gaudy PPFD but never say exactly what color hit that number.
In some cases, it was far red and bleaching plants was the outcome. Others, that high mark was in the green and blue range, which started the "LED cannot grow big buds" that some probably still subscribe to today.

Q.) Why does back crossing make weaker plants?

Backcrossing, the process of repeatedly crossing a hybrid with one of its parents, is a common and powerful technique in plant breeding.1 Its purpose is typically to introduce a specific, desirable trait (like disease resistance) from a "donor" parent into an "elite" or "recurrent" parent while recovering the desirable genetic background of the elite parent.2



However, repeated backcrossing can lead to a phenomenon known as "inbreeding depression," which can result in weaker offspring. Here's why this happens:

• Inbreeding and Homozygosity: Backcrossing is a form of inbreeding. Each time a plant is backcrossed to a single, genetically uniform parent, the offspring become more genetically similar to that parent. This process increases the level of homozygosity, where an individual has two identical copies of a gene at a particular location on a chromosome.
• Masking Deleterious Recessive Alleles: Most plants and animals carry a number of recessive genes that are harmful or "deleterious." In a diverse, outcrossing population, these genes are usually masked because they are paired with a dominant, healthy allele. The individual is a heterozygote and doesn't express the harmful trait.
• Unmasking Deleterious Alleles: As backcrossing increases homozygosity, there's a higher chance that two copies of the same deleterious recessive allele will be paired together. When this happens, the harmful trait is expressed, leading to reduced vigor, smaller size, lower fertility, and other undesirable characteristics. This is a key mechanism of inbreeding depression.
• Loss of Heterosis (Hybrid Vigor): The opposite of inbreeding depression is heterosis or "hybrid vigor," where the first-generation offspring of two genetically different parents are often stronger, larger, and more productive than either parent. This is due to a high degree of heterozygosity, which masks deleterious recessive alleles and can also be attributed to other complex genetic interactions. Backcrossing essentially reverses this process, reducing heterozygosity and causing the loss of hybrid vigor.

It's important to note that backcrossing is a controlled and deliberate process used by breeders to achieve a specific goal.3 By carefully selecting for the desired trait in each generation and continuing the backcrossing process, they aim to recover the elite parent's genetic makeup as much as possible while incorporating only the new gene of interest. However, even with careful selection, the increased homozygosity can still lead to a decrease in overall plant health and vigor.4

I remember breeders rolling with a myth of genetic drift happening from cloning and clones from clones were not desirable, losing potency over time.
Turns out the real culprit was the breeders crossing hybrid after hybrid to the point where so much has regressed. It's like the Romans inventing concrete then the knowledge being lost for almost 2000 years to be reinvented. We have to reinvent hybrids by going back to landrace origins and not current hybrids