Abscisic Acid
(ABA)



ABA's main role is clearly resistance to drought conditions - A Wikimedia Commons Image

Speculative Overall Role: Signal of Water Deficiency



ABA May Figure Prominently in Desert Plants Like Cactus - A Wikimedia Picture

1. Induce by drought.[5]

2. Closes stomata.[6]

3. Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots.

4. Induced by salt stressed plants.

5. Synthesized under heat stress.

6. Induced by cold stress.

7. Inhibits the uptake of Kinetin

8. Down regulates enzymes needed for photosynthesis[7]

1. Actions of ABA attempt to mitigate drought effects.

2. Water loss is slowed by closing of the stomata.

3. Shoot growth does not rectify water deficiency, however, new root growth may.

4. High salt levels may water stress plants.

5. Heat stress may induce water stress.

6. Cold may make water less available to plants.  Transpiration cools plants, so this might be avoided by the ABA induced stomata closing.

8. The photosynthesis process uses twice as much water as it makes.[8]

1. Synthesis: Droughted plants should have high levels of ABA, well watered plants, low levels. Like abundance signals ABA may be mostly made in meristematic cells and much less so as cells mature. (Or for real theoretical beauty, deficiency hormones should be made mostly in mature cells and much less so in meristematic cells).  ABA should be made when a cell has less than enough water to support both it any cell dependent on it for water acquisition.  Thus ABA is an indication that water exists in less than enough amounts to continue the plant at its current size, thus the plant must use emergency stores of water, find new sources of the liquid and cut down on water sinks.

2. Exogenous Treatment: High levels of exogenously applied ABA should induce SA synthesis, because many of ABA's effects may be to increase water levels within the plant, if only temporarily.  This may include making dormant  reactions that are normally dependent on water.

3. Inhibition and Stimulation: ABA should encourage root and new root growth, but inhibit shoot growth and even encourage shoot and leaf senescence.

4. Storage: ABA should cause the emptying of stored water reserves found in vacuoles or tubers.

5. Nutrient and Hormone Attraction and Repulsion: ABA should generally push all nutrients and abundance signals/hormones out of cells.  ABA should attract the deficiency signals/hormones, GA, ET and BA, leading to positive feedback and cell senescence.

6. Apical Dominance: Should break root apical dominance because low water levels are an indication of poor performance by the currently dominant apical root.  ABA may strengthen the currently dominant shoot apex in order not to encourage any new shoot growth which would be a further sink on water levels.

7. Hormone Transport: Water deficiency, on average should be detected in the leaves first, the point furthest from the source of water.  Water may be repelled from tissues high in ABA, thus ABA may be built up in the roots, in order to force water toward the shoots.

8. Cell Division: Although it may encourage it in the roots, if it is inducing new ones, ABA should generally inhibit cell division, as a water deficient plant is in no condition to expand.

9. Senescence: Just as I am hypothesizing that SA, JA, IAA and CK all need to be present to induce cell division, ABA, GA, ET and BA may all need to be present for cell senescence to proceed.  ABA should encourage senescence, particularly of shoot tissue whose nutrients can be cannibalized and used to make more water absorbing root tissue.

10. Specific to a Water Deficiency Signal: Since GA causes lengthening, ET broadening, BA lengthening, what's left is ABA should cause cell and tissue broadening when it induces growth if it does. (I believe I may have seen such a finding but I have to find the reference again).

Jasmonates
(JA)



Jasmonates are similar chemically to prostaglandins, which are chemical messengers found in animals- A Wikimedia Commons Image

Speculative Overall Role:
Signal of Sugar Abundance


JA prompts plants to store excess sugar in tubers like the Potato - A Wikimedia Commons Image

1. "High levels of JA are also found in flowers and pericarp tissues of developing reproductive structures..."

2. High levels of JA exist in the chloroplasts of illuminated plants;^[1]

3. "JA levels also increase rapidly in response to mechanical perturbations such as tendril coiling and when plants suffer wounding."

4. "High levels of JA encourage the accumulation of storage proteins; genes encoding vegetative storage proteins are JA responsive and tuberonic acid (a JA derivative) has been proposed to play a role in the formation of tubers^[4][5]"

5. "JA application can induce chlorosis and inhibition of genes encoding proteins involved in photosynthesis, although the purpose of this response is unknown it is proposed that this response to JA could help reduce the plant's capacity for carbon assimilation under conditions of excess light or carbon^[1]"

6. "The role of JA accumulation in flowers and fruit is unknown; however, it may be related to fruit ripening (via ethylene), fruit carotenoid composition, and expression of genes encoding seed and vegetative storage proteins^[1]"

1. Flowers have high amounts of sugar in order to produce nectar.

2. Chloroplast have high amounts of sugar due to photosynthesis.

3. Bruising and wounding ruptures cells and releases vacuole sequestered sugars.  Also neighboring plant cell reaction to wounding may be to release amylases (by inducing GA?) which increases sugar levels in the inter cell spaces.

4. Storage proteins and tubers are induced by JA in order to store excess sugar.

5. Chlorosis induced by JA, is a negative feedback loop to cannibalize excess photosynthesis machinery.  JA is an indication of excess photosynthesis capacity.

6. Fruits and developing seeds may use JA to store necessary sugar reserves in seeds and fruit.

1. Synthesis: Well lighted plants should have high JA levels, darkened plants should have low levels. JA should be mostly made in meristematic cells and much less so as cells mature.  JA should be made when a cell has more than enough sugar to support both it any cell dependent on it for sugar acquisition.  Thus JA is always an indication that growth amounts of sugar exist and if conditions warrant, that the plant has enough sugar to grow at least in the specific cell where the JA is. (Shoot cells are responsible for acquiring sugar for both it and similar size cells in the root whereas a root cell is only responsible to itself for it own sugar level).

2. Exogenous Treatment: Should induce GA, because JA up regulates various processes limited by sugar levels.  Exogenously applying JA leads the plant to falsely believe that it has high levels of sugar, thus engaging all sorts of reactions that use sugar, thus further depleting what may simply be a homeostatic level of existing sugar and moving this level into the deficiency range.

3. Inhibition and Stimulation: Should Induces new root growth, just like Auxin. If Auxin is also present, JA should inhibit shoot growth because high JA and IAA levels are an indication of at least a short term lack of need to expand the shoots.

4. Storage: should cause sugar to be stored in proteins and tubers for less propitious times.

5. Nutrient and Hormone Attraction and Repulsion: Should attract all nutrients and abundance signals to a cell and repulse deficiency signals.

6. Apical Dominance: Should induce shoot apical dominance along with Auxin, however the possibility exists for two dominant apices if one is particularly good at sugar production (in the light) and one good at oxygen harvesting (in the wind).  May break root apical dominances under conditions of low CK and SA.

7. Hormone Transport: May be expected to travel in the direction of the roots, away from the shoots and particularly the shoot meristems.  Regions of a cell or tissue or plant part that contains high JA, may particularly attract sugar and transport of sugar may follow active JA transport down a plant.

8. Cell Division: Is actually necessary for cell division along with Auxin, Cytokinin and Salicylic acid.  If there are some plant callus lines that will divide with only Auxin and Cytokinin present it is because these cell lines are mutants that produce SA and JA natively, or these other hormones are unknowingly being included with the "other" nutrients/vitamins that are also added to calluses to get them to divide.

9. Senescence: Should protect plant tissue from senescence, particularly root tissue.

10. Specific to a Sugar Abundancy Signal: Because ET and IAA show complimentary growth patterns with ET broadening and IAA lengthening and the same is true for CK (broadening) and BA (lengthening), we might expect that JA should show a complimentary growth pattern to GA's cell lengthening, thus JA should broaden cells and plant tissue.

Gibberellin
(GA)



GA1 - there are many different gibberellin molecules - A WIkimedia Commons Image

Speculative Overall Role: Signal of Sugar Deficiency



The so called "Foolish Seedling" a disease first characterized in Japan which is due to too much GA - Image from here

1. "Gibberellins also reverse the inhibition of shoot growth and dormancy induced by ABA.^[13]"

2. Dissolves stored starch.

3. Inhibits root growth.

4. Promotes shoot lengthening especially in the dark.  Promotes new shoot growth.

1. GA induces shoot growth and breaks shoot growth dormancy to increase sugar levels.

2. GA temporarily increase sugar levels by dissolving stored starch.

3. GA inhibits root growth which is counterproductive to increased sugar levels.

4. GA increases stem length in the dark, to move shoots out of the shade or the ground, into the light and into sugar production.

1. Synthesis: Darkened plants should have high levels of GA, well lighted plants, low levels. Like abundance signals GA may be mostly made in meristematic cells and much less so as cells mature. (Or for real theoretical beauty, deficiency hormones should be made mostly in mature cells and much less so in meristematic cells).  GA should be made when a cell has less than enough sugar to support both it any cell dependent on it for sugar acquisition.  Thus GA is an indication that sugar exists in less than enough amounts to continue the plant at its current size, thus the plant must use emergency stores of starch, find new sources of the molecule and cut down on its sinks.

2. Exogenous Treatment: High levels of exogenously applied GA should induce JA synthesis, because many of GA's effects may be to increase sugar levels within the plant, if only temporarily.  This may include making dormant  reactions that normally depend on sugar.

3. Inhibition and Stimulation: GA should encourage shoot and new shoot growth, but inhibit root growth and even encourage root senescence.  This may be a particularly apparent when ethylene levels are high and ABA and BA levels low as this is an indication that resources need to rerouted from the root to the shoot.

4. Storage: GA should cause the emptying of stored sugar reserves found in vacuoles or tubers.

5. Nutrient and Hormone Attraction and Repulsion: GA should generally push all nutrients and abundance signals/hormones out of cells.  GA should attract the deficiency signals/hormones, ABA, ET and BA, leading to positive feedback and cell senescence.

6. Apical Dominance: GA should break shoot apical dominance because low sugar levels are an indication of poor performance by the currently dominant apical shoot.  GA may strengthen the currently dominant root apices in order not to encourage any new root growth which would be a further sink on sugar levels.

7. Hormone Transport: Sugar deficiency, on average should be detected in the lroots first, the point furthest from the source of wsugar.  Sugar may be repelled from tissues high in GA, thus GA may be built up in the shoots, in order to force sugar toward the roots.

8. Cell Division: Although it may encourage it in the shoots, if it is inducing new ones, GA should generally inhibit cell division, as a sugar deficient plant is in no condition to expand.

9. Senescence: Just as I am hypothesizing that SA, JA, IAA and CK all need to be present to induce cell division, ABA, GA, ET and BA may all need to be present for cell senescence to proceed.  GA should encourage senescence, particularly of root tissue whose nutrients can be cannibalized and used to make more sugar producing shoot and leaf tissue.

Auxin
(IAA and others)



Indol-3-ylacetic Acid , the most common Auxin - A Wikimedia Commons Image

Speculative Overall Role: Signal of Oxygen and Maybe Carbon Dioxide Abundance



Crown galls are caused by Agrobacterium tumefaciens bacteria; they produce and excrete Auxin and Cytokinin and I argue Salicylic acid and jasmonic acid, which interfere with normal cell division and cause largely undifferentiated calluses of cells - A Wikimedia Image (Caption is also partially from Wikipedia - see here)

1. Induce new roots and also promote lateral and adventitious root development and growth

2. Made mostly in meristematic cells decreasing as cells mature.

3. Made in highest amounts shoot apices.

4. Inhibits secondary buds below site of synthesis producing apical dominance.

5. Auxins decrease in light and increase where its dark.

6. Induce cell lengthening.

7. Induce secondary xylem differentiation.

8. Auxins promote flower initiation, converting stems into flowers.

9. When Auxins are no longer produced by the growing point of a plant, this initiates leaf abscission

1. Auxin induces new root growth to compliment oxygen abundance.  Since oxygen is mostly taken in by the leaves, abundance of it shifts growth away from the leaves to roots.

2. ? All the abundance signals are indications that certain meristems are worth sending nutrients to, e.g. investing in, and the strongest candidate in many species wins out to the exclusion of all others.  Although possibly there is one dominant shoot apex for all four nutrient groups, water, minerals, sugar and gases.  Perhaps most of the time, the mineral and water apex and the sugar and gas apices are the same making two dominant apices, one for the root and one for the shoot.

3. Oxygen abundance would be most apparent in that part of the plant producing and harvesting the most amount of oxygen, the leaves.

4. ? Cuts down on excess growth of the shoot.  Excess oxygen already exists, so the mission is that it needs to be complimented by excess sugar, minerals and water.  Perhaps producing these complimentary nutrients is not accomplished by letting secondary shoot buds grow in an uncontrolled way, but by a second shoot apex establishing itself as the best possible site of sugar producing and putting all other resources into establishing productive roots (basically your guess is as good as mine :-).

5. ? Opposite what is expected if speculative overall role is true.  It is known the Auxin is made in the highest levels in the shoot apex and this is often the most light exposed part of the plant.  Perhaps light induces an increase in Auxin biosynthesis, due to the photosynthesis reaction producing oxygen, but that light induces a greater active transport away of Auxin than darkness such that real levels appear to fall in illuminated plant parts.

6. ? Cell lengthening requires processes that require a lot of oxygen? Excess oxygen is sequestered in vacuoles, blowing a cell up like a balloon?

7. ? Opposite of what is expected, unless secondary xylem remains a hollow tube for the transport of oxygen, not the up flow of water.  However, maybe xylem differentiation may be to bring water and minerals to compliment the oxygen indicated by Auxin and the sugar indicated by JA.

8. ? Perhaps flower initiation normally takes a lot of respiration, so point of highest concentration of Auxin, the dominant oxygen apex, is the best place to initiate a flower.

9. A leaf no longer producing Auxin, may no longer be "pulling its weight" in terms of oxygen harvesting and thus needs to be excised.

1. Synthesis: Well aerated plants should have high IAA levels, anoxia treated plants should have low levels. IAA should be mostly made in meristematic cells and much less so as cells mature.  IAA should be made when a cell has more than enough oxygen to support both it any cell dependent on it for oxygen acquisition.  Thus IAA is always an indication that growth amounts of oxygen are being procured by the plant and if conditions warrant, that the plant has enough oxygen to grow at least in the specific cell where the IAA is. (Shoot cells are responsible for acquiring oxygen for both it and some of the oxygen for a similar size cell in the root.  Whereas a root cell is only responsible to itself for it own oxygen level and may even obtain some oxygen from spaces between soil particles).

2. Exogenous Treatment: Should induce ET, because IAA up regulates various processes limited by  oxygen.  Exogenously applying IAA leads the plant to falsely believe that it has high levels of oxygen, thus engaging all sorts of reactions that use O₂, thus further depleting what may simply be a homeostatic level of existing O₂ and moving this level into the deficiency range.

3. Inhibition and Stimulation: Should Induces new root growth, just like JA. Especially if JA is also present, IAA should inhibit shoot growth because high JA and IAA levels are an indication of at least a short term lack of need to expand the shoots.

4. Storage: should cause O₂ to be stored in proteins and tubers for less propitious times.

5. Nutrient and Hormone Attraction and Repulsion: Should attract all nutrients and abundance hormones/signals to a cell and repel deficiency hormones/signals.

6. Apical Dominance: Should induce shoot apical dominance along with JA, however the possibility exists for two dominant apices if one is particularly good at sugar production (in the light) and one good at oxygen harvesting (in the wind).  May break root apical dominances under conditions of low CK and SA.

7. Hormone Transport: May be expected to travel in the direction of the roots, away from the shoots and particularly the shoot meristems.  Regions of a cell or tissue or plant part that contains high IAA, may particularly attract O₂ and transport of O₂ may follow active IAA transport down a plant.

8. Cell Division: Along with  Cytokinin and JA and Salicylic acid, IAA should be necessary for cell division.  If there are some plant callus lines that will divide with only Auxin and Cytokinin present it is because these cell lines are mutants that produce SA and JA natively.  Alternatively these latter two hormones are unknowingly being included with "other" nutrients/vitamins that are also added to calluses to get them to divide.

9. Senescence: Should protect plant tissue from senescence, particularly root tissue.

Ethylene
(ET)



Ethylene is an extremely simple gas - A Wikimedia Commons Image

Speculative Overall Role: Signal of Anoxia/Oxygen Maybe Also Carbon Dioxide Deficiency

1. Broadens/thickens plant parts.

2. Inhibits leaf expansion.

3. Inhibits geotropism.

4. Ethylene is produced at a faster rate in rapidly-growing and -dividing cells, especially in darkness.

5. Induces leaf abscission.

6. Induced by high levels of Auxin, especially in the roots.

7. Induced by flooding.

8. Produces the epinasty reaction where leaf surfaces deliberately grow from a position perpendicular to the stem to one which is more horizontal.

9. Induces root hair growth.

10. Induces prop roots in flooded plants.

11. Induces air spaces in roots during flooding.

1. ? Opposite of what might be expected as generally thin things have more surface area per volume than thick things.  However, perhaps broadening of leaf surface area increases Oxygen uptake, as does growing roots in a lateral direction rather than down.

2. ? Opposite of what might be expected as leaf expansion should increase oxygen absorption.

3. ? Geotropism makes a plant grow upright.  Perhaps growing in a more lateral way could increase oxygen absorption in some circumstances, but I don't know how.

4. Anoxia is most likely to occur in the dark and in metabolically highly active cells which may be typified by rapidly dividing cells.

5. ? Seems counterintuitive.  Should instead preserve leaves since they are the main organ of oxygen production and harvesting.

6. Auxin induces many respiration requiring processes, thus depleting oxygen if Auxin levels get too high.

7. Flooding deprives roots of oxygen they normally take in from between soil particles.  Well aerated soil is best for growing.  Standing water has much less oxygen than well aerated soil.

8. Epinastic leaves act like the handles of water pumps to actively pump up flooded water from roots so that it can be evaporated from the leaves and the roots move away more quickly from being water logged.  Also or may be instead, leaves parallel to the stem have a greater amount of transpiration than leaves perpendicular to the stem because they flap up and down in the wind, which increases evaporation rates.

9. Root hairs absorb more oxygen from the soil more readily.  Also root hairs increase absorption of minerals so we might expect that BA or a better candidate acting as a mineral deficiency hormone should induce this.

10. Prop roots are like snorkels.  They are hollow and let the water logged roots more easily get oxygen.

11. The air spaces induced in roots by flooding serve the same function as above, increasing aeration of the roots.

1. Synthesis: Plants experiencing anoxia should high levels of ET, well aerated plants, low levels. Like abundance signals ET may be mostly made in meristematic cells and much less so as cells mature. (Or for real theoretical beauty, deficiency hormones should be made mostly in mature cells and much less so in meristematic cells).  ET should be made when a cell has less than enough O₂ to support both it any cell dependent on it for O₂ acquisition.  Thus ET is an indication that O₂ exists in less than enough amounts to continue the plant at its current size, thus the plant must use emergency stores of oxygen, find new sources of the molecule and cut down on its sinks.

2. Exogenous Treatment: High levels of exogenously applied ET should induce IAA synthesis, because many of ET's effects may be to increase O₂ levels within the plant, if only temporarily.  This may include making dormant  reactions that normally depend on O₂.

3. Inhibition and Stimulation: ET should encourage shoot and new shoot growth, but inhibit root growth and even encourage root senescence.  This may be a particularly apparent when GA levels are high and ABA and BA levels low as this is an indication that resources need to rerouted from the root to the shoot.

4. Storage: ET should cause the emptying of stored O₂ reserves found in vacuoles or tubers if such things exist.

5. Nutrient and Hormone Attraction and Repulsion: ET should generally push all nutrients and abundance signals/hormones out of cells.  ET should attract the deficiency signals/hormones, ABA, GA and BA, leading to positive feedback and cell senescence.

6. Apical Dominance: ET should break shoot apical dominance because low O₂ levels are an indication of poor performance by the currently dominant apical shoot.  ET may strengthen the currently dominant root apices in order not to encourage any new root growth which would be a further sink on O₂ levels.

7. Hormone Transport: O₂ deficiency, on average should be detected in the roots first, the point furthest from the source of the greatest amount of O₂ (although some O₂ may be absorbed from around the roots).  O₂ may be repelled from tissues high in ET, thus ET may be built up in the shoots, in order to force O₂ toward the roots.

8. Cell Division: Although it may encourage it in the shoots, if it is inducing new ones, ET should generally inhibit cell division, as an O₂ deficient plant is in no condition to expand.

9. Senescence: Just as I am hypothesizing that SA, JA, IAA and CK all need to be present to induce cell division, ABA, GA, ET and BA may all need to be present for cell senescence to proceed.  ET should encourage senescence, particularly of root tissue whose nutrients can be cannibalized and used to make more oxygen harvesting shoot and leaf tissue.

Cytokinin
(CK)



Zeatin - the most common Cytokinin - A Wikimedia Commons Image

Speculative Overall Role: Signal of Mineral Abundance e.g. Nitrogen, Phosphate, Potassium etc.



Cytokinin is synthesized in the greatest amounts in root tips - A Wikimedia Commons Image

1. Induces new shoots.

2. Induces cell broadening.

3. Made mostly in dividing meristematic cells.

4. "Inhibits plant tissue senescence, perhaps more in the shoots than in the roots. New growth and newly-germinated seedlings produce more ethylene than can escape the plant, which leads to elevated amounts of ethylene, inhibiting leaf expansion. As the new shoot is exposed to light, reactions by photochrome in the plant's cells produce a signal for ethylene production to decrease, allowing leaf expansion." (Adedipe, Hunt, & Fletcher)

1. Attempts to compliment root derived mineral abundance with shoot derived nutrients of sugars and gases.

2. ? If BA is CK's compliment this follows the other hormone compliment pairs that show complimentary growth patterns.  CK broadens, BA lengthens, IAA lengthens, ET broadens.

3. CK is a signal that certain meristems cells are good bets for sending resources too.  CK is in effect an indication that these cells are producing the amounts of minerals they supposed to and enough to warrant growth.

4. Preserves shoots in order to compliment minerals with sugar and gases.  May actually inhibit root growth and induce root senescence, just as Jasmonic Acid induces chlorosis.

1. Synthesis: Well fertilized plants should have high CK levels, plants living in poor soils should have low levels. CK should be mostly made in meristematic cells and much less so as cells mature.  CK should be made when a cell has more than enough essential minerals to support both it any cell dependent on it for mineral acquisition.  Thus CK is always an indication that growth amounts of minerals are being procured by the plant and if conditions warrant, that the plant has enough minerals to grow at least in the specific cell where the CK is. (Root cells are responsible for acquiring minerals for both it and similar size cells in the root.  Conversely a shoot cell is only responsible to itself for it own mineral nutrition levels).

2. Exogenous Treatment: Should induce BA, because CK up regulates various processes limited by minerals.  Exogenously applying CK leads the plant to falsely believe that it has high levels of minerals, thus engaging all sorts of reactions that use or are normally limited by mineral levels, thus further depleting what may simply be a homeostatic level of the existing fertilizers and moving this level into the deficiency range.

3. Inhibition and Stimulation: Should induces new shoot growth, just like SA. Especially if SA is also present, CK should inhibit root growth because high SA and CK levels are an indication of at least a short term lack of need to expand the roots.

4. Storage: CK should cause excess minerals to be stored in vacuoles, storage proteins and tubers for less propitious times.

5. Nutrient and Hormone Attraction and Repulsion: Should attract all nutrients and abundance hormones/signals to a cell and repel deficiency hormones/signals.

6. Apical Dominance: Should induce root apical dominance along with SA, however the possibility exists for two dominant apices if one is particularly good at fertilizer absorption (in good soil) and one good at water harvesting (in the moist part of the soil).  CK may break shoot apical dominances under conditions of low JA and IAA.

7. Hormone Transport: CK may be expected to travel in the direction of the shoots, away from the roots and particularly away from root meristems.  Regions of a cell or tissue or plant part that contains high CK, may particularly attract fertilizer type minerals and transport of important minerals may follow active or passive CK transport up a plant in the xylem or other tissue.

8. Cell Division: Along with  IAA and JA and Salicylic acid, CK should be necessary for cell division.  If there are some plant callus lines that will divide with only Auxin and Cytokinin present it is because these cell lines are mutants that produce SA and JA natively.  Alternatively these latter two hormones are unknowingly being included with "other" nutrients/vitamins that are also added to calluses to get them to divide.

9. Senescence: Should protect plant tissue from senescence, particularly shoot tissue.

Brassinolides
(BA)


Brassinolide was the first Brassinosteroid discovered - A Wikimedia Commons Image

Speculative Overall Role:
Signal of Mineral Deficiency e.g. Nitrogen, Phosphate, Potassium etc.


Brassinosteroids were first discovered in Brassinus napus, Rapeseed, from which comes Canola Oil (from a variety). Brassins are from the Mustard Family - A Wikimedia Commons Image

1. "One well-supported hypothesis is that all tissues produce BRs, since BR biosynthetic and signal transduction genes are expressed in a wide range of plant organs, and short-distance activity of the hormones also supports this.^[4][5]"

2. Promote differentiation of xylem tissues

3. Inhibit leaf abscission.^[14]

4. Plants found deficient in brassinolides suffer from dwarfism.

5. Promotes cell expansion and cell elongation;^[4] works with Auxin to do so^[6]

6. Accelerates senescence in dying tissue cultured cells; delayed senescence in BR mutants supports that this action may be biologically relevant^[4]

7. Can provide some protection to plants during chilling and drought stress^[4]

8. BA is transported acropetally.

1. ?

2. Stimulates phloem growth in order to route sugar to a plant part experiencing deficiency.

3. BA does this to maximize the level of sugar coming from the leaves. Leaf abscission would cut down on some sugar production.

4. Brassinolide encourages stem lengthening just like Gibberellin, because the  signal could be an indication the plant's leaves are in the shade and thus the stem needs to lengthened to move it back into the sun.

5. ?

6. All the deficiency hormones should speed senescence in those plant parts that are sinks and net users of their respective nutrients, but should preserve those plant parts that are harvesters or net producers of the nutrients they represent.

7. All the deficiency hormones may do this by causing plant cells to either senesce (if they are in bad shape) of go into hibernation.

8. Most sugar deficiencies should occur in the roots, so this make sense.

Note BA actually appears to be involved in the GA pathway whether as the principal and GA being a secondary messenger or vice versa.  From the evidence BA is like GA, actually appears be a sugar deficiency hormone. 

1. Synthesis: If BA is a sugar deficiency signal, plants grown in the shade or with a lot of darkness, should have high levels of BA.  Alternatively well illuminated plants should show low levels. BA should be made when a cell has less than enough sugar to support both it any cell dependent on it for sugar acquisition.  Thus BA is an indication that sugar levels exists in less than enough amounts to continue the plant at its current size, thus the plant must use emergency stores of sugar (starch), find new sources of light and cut down on the sugar sinks, by for instance inhibiting root growth.

2. Exogenous Treatment: If BA is truly a sugar deficiency hormone, high levels of exogenously applied BA should induce JA synthesis, because many of BA's effects may be to raise sugar levels within the plant, if only temporarily. 

3. Inhibition and Stimulation: BA should inhibit root and new root growth and even encourage root senescence.  It should encourage shoot growth, preserve leaves from senescing and even encourage new shoot growth initiation.  This may be a particularly apparent when ABA levels are low and GA and ET levels high as this is an indication that resources need to rerouted from the shoot to the root.

4. Storage: If BA is really a sugar deficiency signal, it should cause the emptying of stored starch reserves found in vacuoles or tubers if such things exist.

5. Nutrient and Hormone Attraction and Repulsion: BA should generally push all nutrients and abundance signals/hormones out of cells.  BA should attract the deficiency signals/hormones, ABA, GA and ET, leading to positive feedback and cell senescence.

6. Apical Dominance: BA should break shoot apical dominance because low sugar levels are an indication of poor performance by the currently dominant apical shoot.  BA may strengthen the currently dominant root apice in order not to encourage any new root growth which would be a further sink on essential sugar levels.

7. Hormone Transport: sugar deficiency, on average should be detected in the roots first, the point furthest from the source of mineral harvesting_, the shoot. 

8. Cell Division: Although it may encourage it in the shoot, if it is inducing new ones, BA should generally inhibit cell division, as a sugar deficient plant is in no condition to expand.

9. Senescence: Just as I am hypothesizing that SA, JA, IAA and CK all need to be present to induce cell division, ABA, ET , BA and GA (with BA and GA working together) may all need to be present for cell senescence to proceed.  BA should encourage senescence, particularly of root tissue whose nutrients can be cannibalized and used to make more shoots.

10. Specific to a Sugar Deficiency Signal: Should induce C4 photosynthesis which is a more efficient but more risky form of photosynthesis/sugar making.  It's more risky because it causes the buildup of poisons in the plant.

11. GA and BA may be part of the same chemical hormone cascade pathway.