Cascade Analytical's Leaf Notes 1997

The Heart of the Matter - (leaf Notes 1997)
Trees are vascular plants, which means that they have specialized conductive tissues that act like pipelines to move nutrients and water from root to shoot. The first type, phloem, carries carbohydrates (CHO) produced during photosynthesis in the leaves, down to the shoots and roots for growth and storage. This tissue makes up the cambium of the tree and is located just beneath the bark. The second type, xylem, transports water and soluble nutrients from the roots up into the aerial parts of the plant for use in photosynthesis. The xylem makes up the structural wood of the tree. "Rings" in the wood of a tree are the xylem cells produced during a growing season. In older trees, the xylem which no longer functions is called the "heartwood" of the tree.

Transportation For Evaporation! (leaf Notes 1997)
If it is not dissolved in water, it just isn’t going to get there. Nutrients in the soil are only available to the tree if they are dissolved in water (soil solution) and once the nutrients are in the tree, water continues to play the leading role in nutrient transport. Proper water management, evident as adequate water supply to the trees, is the key to a healthy and productive orchard.

Water and soluble nutrients are pulled through the tree as water evaporates through the leaves (evapotranspiration). Water loss In a mature tree can be as high as 20-50 gallons per day! Water stress in the tree inhibits photosynthesis (energy source) and nutrient flow (primary units of photosynthesis). Any horticultural practice or climatic stress which reduces photosynthetic rates (CHO production) will ultimately effect fruit quality, making water management one of our most critical horticultural practices.

It's A "Sink"-ing Relationship - (Leaf Notes 1997)
The relationship between source (production) and sink (use) explains how a healthy tree can produce poor quality fruit! "Sources" are generally mature photosynthetic (CHO producing) leaves. "Sinks" or major users of CHO are the fruits, roots, and immature leaves. The vascular system connecting the "sources" to the "sinks" is the phloem tissue located directly beneath the bark of the tree (cambium).

Several factors influence the demand of a sink and what priority it has over various other sink tissues. First, the proximity of a source to a sink is important and the two must be connected directly by vascular tissue. Second, transport to sink tissue is energy dependent.

Where sink activity = rate of uptake of CHO per unit weight of sink tissue and
sink size = total weight of sink tissue.

So, how does this relate to a healthy tree and poor fruit quality? It appears that for many reasons, fruit are weak sinks and the vegetative growth of a tree has a much stronger pull for carbohydrates (CHO) than fruit, making fruit the last priority for phloem sap. The relationship of carbohydrate production by the "source" and the demand at the "sink" becomes increasingly important when the cambium tissue of a tree has been damaged (i.e. winter, rodents). A damaged cambium results in less flow through the phloem creating greater competition for less sap. Since fruit is such a weak sink, this can result in less productive trees or small fruit!

Did you know ... The demand exerted by the sink tissues can have a direct effect on the photosynthetic rate? When the demand is high, the movement of the sap (photosynthetic products) can be up to 1 meter per hour!

Where Did All The Calcium Go?! (Leaf Notes 1997)
Calcium is generally not a nutrient that is lacking in the soil, but it is the culprit of many fruit disorders. So, what seems to be the problem? The answer lies within. The tree may be taking up enough calcium, but the calcium is not being allocated to the fruit. This problem stems from the uneven distribution of calcium within the tree.

Calcium is absorbed by the roots in ionic form (Ca++). Calcium is primarily distributed throughout the tree via the xylem. Therefore, it does not follow the source to sink relationship seen in phloem transport. Rather, it is pulled to tissue by their rate of transpiration (how fast water evaporates through the surface of the tissue). This creates some problems for fruit when it comes to acquiring nutrients in the transpiration stream. Storage organs, such as fruit, have a high demand for nutrients but a low rate of transpiration. On the other hand, vegetative tissues have a high transpiration rate. This creates a stronger pull for the xylem flow. Vegetative tissues are able to out compete fruit for nutrients in the xylem because of the higher rate of transpiration. This can leave fruit thirsting for more when it comes to nutrients such as calcium!

Metallic dimethyldithiocarbamates (Fe, Mn, Zn); ethlylene bisdithiocarbamate sales (disodium; diammonium; potassium ammonium; zinc, manganese) metalc bases attached to dithiocarbanic acid. Add this to the list of potential "contaminants" of leaf analysis, Ziram was last year’s "culprit". Evident as enriched amounts of Zn/Mn present in leaves, not explained by else.

Remember the Nutrition Short Course of 1983 (Leaf Notes 1997)
If you do, your age is 40 something. Dr. Uriu brought to our attention the "backflow" concept. Backflow is explained: "as the leaf grows in size, there is a steady accumulation of nutrients in the leaf until about mid summer, after which the amount in the leaf remains fairly constant. As senescence approaches, there is a general breakup of organic materials making many constituents, including mineral nutrients, more soluble. These materials migrate out of the leaves and into the stem in a backflow phenomenon."

The amount of nutrient moving out of the leaf and into the stem in the backflow mechanism can be quite substantial. The table below summarizes data found in the literature indicating the actual quantities.

Nutrient	Apple	Apple	Peach	Pear	Pistachio
	1931	1953	1958	1970	1976
	Murneek	Batjer	Westwood	Uriu	Crane
N	34-40%	60%	67%	57%	70%
P	---	60%	67%	60%	70%
K	---	30%	35%	22%	50%
Mg	---	---	---	22%	25%
Ca	---	---	---	15%	15%

"The backflow phenomenon acts as a conservation mechanism in that all of the nutrient in the leaves are not lost with the falling leaves. Some of the nutrients go back into the tree before leaf detachment. It can also be presumed that the higher the level of the nutrients in the leaf prior to leaf fall, the higher the actual amount of the nutrients which "backflow" into the tree, thus increasing the reserves of a specific nutrients available for the following season."

Synopsis of Ammonium vs. Nitrate & Rootstock Effect on Apple Flowering.
Gao etal., JASHS/1992
Contributing Client: Dr. Randy Lee, Washington Fruit & Produce

Three (3) rootstocks commonly used in the NW are compared under different fertilizer regimes. Uniform "Fuji" are grafted on different rootstock and grown 1 year. Planted in coarse sand in 1.6 gal containers, cut back to 20". Fertilized with either ammonium nitrate or equal amounts of N from both ammonium and nitrate (Table 1). All other essential elements were supplied at equal rates. The fertilizer was applied in 1 quart doses twice per week April 10 through August 30. One year shoot growth and bloom data are presented in Tables 2 & 3.

	Nitrate	Ammonium	NH₃ + NO₃
Ammonium Sulfate	---	264	132
Calcium Nitrate	472	---	236
Calcium Sulfate	---	344	172
Potash Phosphate	87	87	87
Magnesium Sulfate	185	185	185
Iron	3	3	3
Boron	0.5	0.5	0.5
Manganese	0.5	0.5	0.5
Zinc	0.5	0.5	0.5
Copper	0.02	0.02	0.02
Molybdenum	0.01	0.01	0.01

Observations -
Trees were watered as needed. After one week, leachate from the bottom of pots shifted:
        from pH 6.0-7.5 with nitrate only
        from pH 6.0-5.5 with ammonium only
        remained the same with ammonium nitrate

	M7	MM106	M29
		Total shoot growth	(inches)
Nitrate (NO₃)	128.4	113.1	109.9
NH₄ + NO₃	105.6	122.1	102.0
Ammonium (NH₄)	82.3	91.4	64.6
		Number of side shoots
NO₃	6.4	4.8	5.1
NH₄ + NO₃	6.0	5.5	5.3
NH₄	8.9	8.8	7.3
		Mean internode length	(inches)
NO₃	0.946	0.906	0.946
NH₄ + NO₃	0.946	0.827	0.946
NH₄	0.709	0.709	0.630

Observations - Nitrate encourages terminal growth and internode spacing. ammonia encourages lateral initiation.

	M7	MM106	M26
		Number of terminal flower buds
Nitrate (NO₃)	0.9	2.4	1.7
NH₄ + NO₃	1.4	2.6	1.4
Ammonium (NH₄)	1.9	2.4	3.2
		Number of auxiliary flowering buds
NO₃	4.6	9.7	4.4
NH₄ + NO₃	7.7	12.2	10.0
NH₄	13.7	16.9	14.0
		Flowering bud as % of emerged buds
NO₃	7.4	11.5	5.5
NH₄ + NO₃	8.2	24.1	11.8
NH₄	20.7	29.0	22.7

Observations - Ammonium form of fertilizer has a dominant effect (direct) on flowering.

This article is an excerpt from the Proceedings of the Twelfth Annual Postharvest Meeting 1996 on How Preharvest Factors Present Postharvest Problems, written by Drs. E. Fallahi, G. A. Lee, and J. K. Fellman.

The use of preharvest minerals for predicting postharvest fruit quality is a relatively unused but vital tool in the state of Washington State apple industry. Although leaf analysis is a diagnostic tool for optimizing mineral nutrition in fruit trees, it is not a strong tool for predicting fruit quality (Fallahi et al., 1985: Sharples, 1980) and storage disorders (Bramlage et al., 1980: Sharples, 1980). Understanding the relationships between postharvest quality and preharvest mineral nutrients and orchard practices makes various management decisions, such as storage strategies, easier. If the apple industry can predict and categorize fruit likely to be low or high in some postharvest quality parameters prior to storage, profit can be enhanced. A perfect identification and prediction of fruit quality is neither possible nor absolutely necessary. Sharples (1980) presented fruit mineral standard for Cox's Orange Pippin apples, suggesting that the performance of fruit in storage can be predicted by fruit analysis immediately before harvest. What must be emphasized is the continued communication to the laboratory after storage to complete the data base circuit.

Fallahi et al (1985) studied the relationships between seasonal fruit and leaf contents and fruit quality in Starkspur Golden Delicious apple. Regression equations from seasonal leaf and fruit mineral analyses were developed to predict fruit quality parameters at harvest and after storage. In this report, although between-year predictions were not as good as within-year predictions, regression equations could successfully place fruit in high or low categories for most quality parameters.

Fallahi et al. (1988) then developed a procedure to strengthen fruit quality prediction between years. In their diagnostics procedure, leaf and fruit mineral levels were ranked from 0 to 100 basic (percentile), and mineral nutrient factors limiting apple and pear fruit quality were identified. In this procedure, an individual can decide which quality parameters are important and whether minimum, maximum, or intermediate values for these quality parameters are most desirable. These quality parameters were then ranked relative to each other. Using a simple sorting program allows the operator to use these rankings to choose desirable categories of fruit. This ranking procedure was tested with various sets of data on apples and pears. The percentile approach reported by Fallahi et al. (1988) allows meaningful interpretation despite large differences in fruit mineral concentrations reported for different locations and years by a range of analytical laboratories. The procedure is flexible and fruit could be categorized successfully according to several definitions of optimum quality.

Bramlage et al. (1983 and 1985) studied the relationships between mineral nutrients and postharvest disorder of Macintosh apple over several seasons. They reported that Ca was the most variable element among samples within seasons. They found that the lower the Ca level the higher the incidence of breakdown, rot, and scald. In their report, susceptibility of fruit to breakdown was predicted from mineral analysis of fruit two weeks before harvest (Bramlage et al., 1985).

The ratio-based Diagnosis and Recommendation Integrated System (DRIS) approach has also been used in apple to study the associations between fruit mineral, particularly Ca and N with only a limited success (Fallahi and Righetti, 1984). This is likely due to the fact that the DRIS focuses on quantity, where fruit mineral analysis is a focus on quality.