Early Application of Ethrel Extends Tomato Fruit Cell Division and Increases Fruit Size and Yield with Ripening Delay. Condensed from the link below. Note: this applies equally well to pumpkins and other seed baring fruit...
Fruit expansion in tomato can be divided into two general phases. The initial phase of expansion occurs during approximately the first week after pollination and reflects a period of active cell division. The second phase is completed by approximately the 100th day or later stage and is characterized by extensive cell expansion and very little cell division. Ethylene, is a plant growth gaseous hormone. It can be produced by almost all parts of higher plants, though the rate of production is highest where cell division occurs (Newly pollinated fruit). Its production is increased during leaf fall, flower senescence and fruit ripening. In addition, stress factors such as wounding, flooding, chilling, disease, high temperatures and drought seem to induce ethylene synthesis.
So why is it important at fruit set.....Simply because it helps to increase cell division.... Studies have shown the fruit period of cell division can be extended up to 16-18 days after pollination with applications of ethylene... fruit response to early ethylene treatments noted that sinks became significantly larger in size and heavier in weight with a ripening delay of about 10 and 15 days compared with those of controls.... This suggests that ethylene regulates tomato fruit transmission from cell division to cell enlargement. In addition, fruit cell division is terminated only when internal ethylene decreases to its normal basal level, allowing cell enlargement to dominate and proceed as in the case of the early applications will result in bigger fruit.....
The ripening delay of ethylene treated fruits may be caused by the longer time required for the increased cell number to reach maturation. A low level of ethylene application at the tomato early fruiting stage can be used for increasing fruit yield by increasing fruit size and consequently its quality.....
Pruning for cell division maximizes fruit growth.
Published by: Maximum Yield, USA
By Russ Landry
aka > Rocco Brewer
When we prune or top off plants it is really about removing faster growing shoots. Pinching off can be referred to as removing Apical Dominance (AD). This is essentially removing the topmost shoot or main stem of a plant and forcing the remaining growth points to produce and grow faster.
AD is controlled by the production of a plant growth hormone called auxin that is developed in the plants leading shoots. These auxins in higher concentrations inhibit and slow the growth of other side branching and lateral shoots. So AD gives plants their traditional triangular shape or Christmas tree look.
The removal of this top most dominant shoot, results in a lowering of growth inhibition throughout the rest of the parts of the plant. Effectively it turns the lights on for other parts of the plant. So this allows new lateral side shoots to be produced that are more vigorous, lengthy and bushy in density. The effect forces the lower branches and architecture of the plant to become stouter instead of being restricted by the apical dominance of the inhibitory main vine or shoot. Simply the other parts the plant become more hearty than normal. The result is a plant that has more a full-bodied vascular system. Therefore apical pruning changes the basic design of sink, source relationship. The channels and pathways leading into the potential new fruit of the other parts of the plant develop bigger than they normally would have become. So that's the simple reason why the excessive pruning of annual fruiting plants is very successful. Forcing the plants vascular systems and structures to grow bigger therefore signals fruit to develop as bigger and thus become larger more robust sinks.
Pruning has three main goals or benefits. One in controlling the direction of growth and two in encouraging vigorous new growth of side shoots. However a third little understood benefit to removing apical growth is increased yields. Removing apical dominance just before the fruiting buds begin to develop can enhance yields.
During growth young tender fruit buds demand much of the plants resources. It is thought that removing AD stimulates development of cell division in branches leading into fruiting trusses or pedicles. This may be in part be caused by the release of Ethylene from wound injury sites. These trusses now are able to develop into larger functioning Xylems and Phloem’s that can allow the greater import of carbons from the leaves. What this means is that the combined potential of more cells may translate into greater expansion potential of the fruit. This has been documented in findings that larger fruit were benefactors of increased cellular composition.
The take home message here is a fruit that has more cells ultimately has more expansion potential regardless of a plants size. If you are busy growing leaves you’re never going to have the necessary cellular division to drive fruit yields to their maximum or epigenetic potential.
So no we’ve reached a point of enlightenment what can a grower do to enhance fruit size and increase yield. Firstly it is important that in most fruiting annuals all shoot growth be halted at the beginning stage of flowering and fruiting growth. This will help to ensure there is no competition for immature young fruitlets. Secondly helping the fruit or its truss to grow and have its cells divide for a longer period time is critically important.
Typically cells within fruiting bodies will divide for a limited time period.
Fruit development occurs in four phases,
1. fruit set,
2. a short period of rapid cell division
3. a longer cell expansion phase
4. ripening or maturation stage
Research has proven that it is possible to stimulate extended periods of cell division. This has been demonstrated in applying ethylene during the fruits early growth period, immediately after pollination. The exact cause as to why Ethylene drives that rate of cell division is unknown. However one response is a stress protection factor that may signal a genetic trigger. This signal may boost increased cell production to safeguard the fledgling seeds of the next generation with a larger protective envelop or fruit outer shell.
The rate and duration of cell division varies among fruits and also among tissues within a fruit. However the cell division phase gradually shifts fruit into the cell expansion phase of increased outer shell girth. Cell division seems to be more critical than cell expansion in determining final fruit size. Generally the more cells a fruit has the larger its final size will be.
During peak fruit expansion, there is an intense flow of photo assimilates from mature leaves (sources) into rapidly enlarging fruit (sinks). Sugars generated by photosynthesis, along with amino acids Calcium and other nutrients move via the enlarged phloem into the ever enlarging fruit.
The relative strength of source and sink is a major factor for enlargement of fruit. Enhanced transport is dictated by cell divisions which have stout vascular connections. During plant growth, xylem and phloem enlargement occurs in an orderly and patterned manner of superior vascular connections.
Therefore in a nutshell if you build a bigger house the youngsters inside will be afforded greater protection. Of course to a grower this means maximum yields and greater fruit size. One other benefit that comes along with building a bigger house is that it often takes longer to ripen and mature a fruit that has a robust architecture. This effect further enhances fruit size and yield as slowing or delaying death and senescence of the main parent plant hinders aging and lengthens the growth period.
So if you want the largest yield possible it is absolutely imperative to increase the length of time cells divide in the fruit after pollination.
Helping you grow bigger fruit.
Key Words : Apical Dominance, Cell Division, Pruning.