After having a couple of discussions with a couple of ICmag'ers, I thought I would post a thread for a nutrient toxicity none of us had ever seen in cannabis: boron.
Below is my current nutrient test mix, I messed up in finding ppm of B from boric acid. When converting to decimal from percent I converted 17.48% to 0.01748. So, I recently used 7.09 ppm B, but I was trying to use ~0.86 ppm B. Boric acid, when mixed with water, provides B that is immediately available to the plants.
I should have used 0.015 g (15 mg) of boric acid per gallon, for a total of ~0.86 ppm, not 0.15 g (150 mg) of boric acid per gallon for a total of ~7.09 ppm.
The soilless solution pH is ~6.0-6.15 and EC was ~0.98 using PourThru method from North Carolina State University. The pH and EC readings accounted for water temperature.
There are two expressions of B toxicity in plants: (1) yellowing and burn of leaf tips and edges in older leafs; and (2) die back of young leafs and meristem(s). The former is for plants were B is immobile and latter is for plants where B is mobile.
I am pretty sure B is immobile in cannabis, as it is for most species. For species where B is mobile, the plant produces polypols[1] and moves complex sugars (ex., sorbitol) through phloem[2]. I spent the past little while trying to find if cannabis produces polypols and moves complex sugars; I haven't found anything yet. If anyone has any info I would love to read up.
At this point I think B is immobile in cannabis, esp. because of the classic B-immobile toxicity symptoms my plants are showing. The only other thing it could be is my use of yucca extract, which has never done this, but I did use 3.5 ml/gal instead of 2.5 ml/gal.
Boron toxicity in plants not considered boron-tolerant often begins about 2 ppm. About 0.5-1 ppm B is a good goal for fertigation.
Boron is an anion, which means it is easily flushed from soilless solution. If the media has low AEC (anion exchange capacity), for example, due to lack of certain clays particles and powders, humus, etc.
Pics:
Toxicity symptoms for B-mobile plant (Ligustrum) and B-immobile plant (Strawberry):
Concentration by ppm of B at various areas of leaf, for B-mobile Plant (Apple) and B-immobile plant (Walnut):
Toxicity symptoms in alfalfa, a B-immobile plant:
Toxicity symptoms in pistachio, a B-immobile plant:
Deficiency symptoms in tomato, a B-immobile plant (by ppm):
Leafs from my plants after 7 ppm B, it starts at older-middle leaves, not at very top and not at very bottom (pics aren't the greatest, they are from my camera phone):
References:
Below is my current nutrient test mix, I messed up in finding ppm of B from boric acid. When converting to decimal from percent I converted 17.48% to 0.01748. So, I recently used 7.09 ppm B, but I was trying to use ~0.86 ppm B. Boric acid, when mixed with water, provides B that is immediately available to the plants.
I should have used 0.015 g (15 mg) of boric acid per gallon, for a total of ~0.86 ppm, not 0.15 g (150 mg) of boric acid per gallon for a total of ~7.09 ppm.
The soilless solution pH is ~6.0-6.15 and EC was ~0.98 using PourThru method from North Carolina State University. The pH and EC readings accounted for water temperature.
I am pretty sure B is immobile in cannabis, as it is for most species. For species where B is mobile, the plant produces polypols[1] and moves complex sugars (ex., sorbitol) through phloem[2]. I spent the past little while trying to find if cannabis produces polypols and moves complex sugars; I haven't found anything yet. If anyone has any info I would love to read up.
At this point I think B is immobile in cannabis, esp. because of the classic B-immobile toxicity symptoms my plants are showing. The only other thing it could be is my use of yucca extract, which has never done this, but I did use 3.5 ml/gal instead of 2.5 ml/gal.
Boron toxicity in plants not considered boron-tolerant often begins about 2 ppm. About 0.5-1 ppm B is a good goal for fertigation.
Boron is an anion, which means it is easily flushed from soilless solution. If the media has low AEC (anion exchange capacity), for example, due to lack of certain clays particles and powders, humus, etc.
Pics:
Toxicity symptoms for B-mobile plant (Ligustrum) and B-immobile plant (Strawberry):
Toxicity symptoms in pistachio, a B-immobile plant:
Deficiency symptoms in tomato, a B-immobile plant (by ppm):
Leafs from my plants after 7 ppm B, it starts at older-middle leaves, not at very top and not at very bottom (pics aren't the greatest, they are from my camera phone):
References:
[1] "Redefining Boron Toxicity Symptoms in Some Ornamentals"
Patrick H. Brown, Hening Hu and Warren G. Roberts
Slosson Report 95-98 1
(full text) http://slosson.ucdavis.edu/newsletters/Brown_199829071.pdf
[2] "Topic 5.1 Symptoms of Deficiency in Essential Minerals"
Wade Berry, UCLA
A Companion to Plant Physiology, Fifth Edition by Lincoln Taiz and Eduardo Zeiger
[Boron] http://5e.plantphys.net/article.php?ch=3&id=289
[3] "Chapter 12 Boron toxicity"
Ross O. Nable, Gary S.Banuelos, and Jeffrey G. Paull
Plant and Soil 193: 181–198, 1997
http://www.plantstress.com/articles/toxicity_i/boron.pdf
[4] "Boron Mobility and Consequent Management in Different Crops"
By Patrick H. Brown and Hening Hu
Better Crops/Vol. 82 (1998, No. 2)
http://www.back-to-basics.net/fertilityfacts/pdf_files/boron_mobility.pdf
[5] "Boron Toxicity Symptoms"
http://www.eplantscience.com/botani...ts_micronutrients/boron/toxicity_symptoms.php
Patrick H. Brown, Hening Hu and Warren G. Roberts
Slosson Report 95-98 1
(full text) http://slosson.ucdavis.edu/newsletters/Brown_199829071.pdf
[2] "Topic 5.1 Symptoms of Deficiency in Essential Minerals"
Wade Berry, UCLA
A Companion to Plant Physiology, Fifth Edition by Lincoln Taiz and Eduardo Zeiger
[Boron] http://5e.plantphys.net/article.php?ch=3&id=289
[3] "Chapter 12 Boron toxicity"
Ross O. Nable, Gary S.Banuelos, and Jeffrey G. Paull
Plant and Soil 193: 181–198, 1997
http://www.plantstress.com/articles/toxicity_i/boron.pdf
[4] "Boron Mobility and Consequent Management in Different Crops"
By Patrick H. Brown and Hening Hu
Better Crops/Vol. 82 (1998, No. 2)
http://www.back-to-basics.net/fertilityfacts/pdf_files/boron_mobility.pdf
[5] "Boron Toxicity Symptoms"
http://www.eplantscience.com/botani...ts_micronutrients/boron/toxicity_symptoms.php