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A Trip up the Calcium Highway: The Next Chapter

Spring 2011 GVGO Science News
By: Russ Landry

Most of us know the most frustrating events in growing the Atlantic Giant Pumpkin (AGP) can occur usually in the dog days of August. Blindsided growers are left empty handed by the affects of a simple diminutive tiny atom on the periodic table of elements. The event can play a cruel an extremely doubtful havoc on a plant’s single fruit. So traumatic it can force a grower to abandon the hobby for much more benign chores around the yard.

Consider that each plant requires an hour a day of care or more from spring through to fall including prep time. It becomes easy to understand the investment that a grower places with each seedling placed into the patch.

A mere lack of small a quantity of this lowly common atom can very easily destroy the best of fruit within the blink of an eye. The misshapen fruit often sends the grower reeling and wanting for another opportunity to grow a big pumpkin.

This pesky substance known as Calcium (Ca) for centuries is really rather ambiguous. Ca is slivery, grey and dull in colour with little value to mankind. It is easy to see why it never gained acceptance adorning a cavewomen’s appendages. However Ca is the fifth most abundant element in the earth’s crust. Found mostly as limestone and gypsum Ca was quickly put to use by plants as they colonized the earth’s early land masses.

Cavemen first noticed it as icicle looking stalagmites and stalactites which are formed of calcium carbonate. It is also an essential component of animal’s bones, teeth and sea shells. Ca is an alkaline metallic mineral know to moderate and neutralize acids. Not considered a major plant element required for growth it is essentially a macro element in the giant competitive growers pumpkin patch. Truly this obscure mineral holds the super power of kryptonite in the gardens, giant pumpkin patch.

However Ca is highly susceptible to localized restrictions that prevents uptake into the roots. This can be caused either by poor soil moisture levels, displacement of competitive cations or lock up caused by bicarbonate molecules. Highly soluble Ca moves within the soil solution around the root zone awaiting transport up into the plants calcium highway we call the xylem.

Taken in by the plants roots it is transformed into calcium pectate. Distributed amongst plant in the xylem flow it accumulates within the plants vascular systems including the leaves and fruits cell walls. Sadly for those who have faced its ugly wrath an unhealthy portion of Ca results in a smiling pumpkins distal cellular walls.

Krytonitic power is of course an understatement for a grower of Atlantic Giants. Most are keenly aware of the balance of power that Ca plays in the soil. Firstly it helps to nullify the affects of soil acids by lowering pH. Secondly it competes with other cations in the soil and helps to maintain an appropriate balance within the soils elemental substructure. The discovery of Ca’s importance in the role of growing an AGP is not new. Related vegetable growers and scientists alike have understood its presidential role and function in plants for many decades.

The pumpkin community often begs for a greater understanding and investigation. Exploring the correct soil proportions of Ca but also to the science of its uptake and induction into the living plant is necessary. If Fruit Sinks (FS) of rapidly expanding cucurbita maxima are to surpass 2000 pounds these two questions must be answered.

The main causes for concern are reduced Ca uptake resulting in blossom end split (BES) and low fruit weights. Most soils are readily abundant in the alkaline mineral and often at very high levels. However, much of the calcium in your soil is often tied-up in insoluble compounds and is unavailable to be absorbed by plant roots. Ca is usually very mobile in the soil and is easily absorbed into young unsuberized roots. It is transported within the plants main highway known as the xylem through a process called transpiration. Fresh supplies of water and Ca are carried up this one-way highway within the transpiration stream to the more dominate evaporative parts of the plant. Often this happens to be the leaves which tend to transpire larger amounts of water and thus receive the lion’s share of Ca.

The most critical time for the fruit is in early stages of development when the fruit develops its internal distribution network. It is at this time when young developing blossoms and fruit suffer during periods of evaporative or uptake stress, setting the stage for a growers blossoming demise.

Low fruit weights and BES often begin to develop during the first few days before and after pollination setting the stage for rigid blossom end walls of seasoned fruit. Related to BES, Dill Rings, Sag Lines and internal wall cracks are latter stage effects of water supply and Ca uptake stress.

Trying to identify some of the more popular theories and ideas surrounding the cause of these events is often the most misunderstood of pumpkin deformities. Here are a few of the causes and tips I have referenced over the past several years from hundreds of research journals and articles I have reviewed.

Low fruit weights, Blossom-end splitting, Dill Rings and internal cracking are not caused by a parasitic organism. The conditions are caused by physiologic disorders associated with low concentrations of water, Ca and nutrient products in the xylem flow. The effects can be triggered by environmental factors that surround the roots and or the leaf canopy.

Calcium is required in relatively large concentrations for normal cell growth. When a rapidly growing fruit is deprived of necessary water and Ca, the tissues degrade. BES, Dill Rings and internal wall case cracks are induced when demand for plant water exceeds supply. Split event dates are often proceeded by a prior periods of water supply stress. Even with an abundance of calcium in the soil, inadequate calcium levels in the plant and fruit can occur under these conditions.

This may also result from a host of conditions including high amounts of competitive cation’s in the soil, high organic matter, drought stress, excessive soil moisture or wide fluctuations which reduce uptake. Evaporative leaf canopy stress contributes by increasing the demand for xylem flow and Ca when it may not be available in larger quantities for transportation to the fruit. Therefore reduced movement of Ca into the plant are major concerns.

Incomplete Conclusions