principles of fruit production (pomology 16201) chapter 1...

Prof. Dr. Atef M. Ibrahim Alexandria University Pomology 16201 (Principles of fruit production) Faculty of AgricultureSecond Level Students Pomology Department

Principles of Fruit Production (Pomology 16201)

Chapter 1

(First lecture)

Definitions:

1. Agriculture: The business or science of raising plant & animal products from the

land …or it is the science, the art and the technique of supplying human wants with

the products of soil.

2. Horticulture: It is the agriculture science that deals with the production, utilization

and improvement of fruits, vegetables and ornamental plants. The term is derived

from the Latin word hortus that means "garden", and cultura that means

"cultivation".

3. Pomology (Fruit Science): The branch of horticulture concerned with the production

of fruit crops. The term is derived from the Latin word Pomum: fruit, and Ology:

science.

Purposes of studying Pomology 201

1. To know and understand the different cultural practices required for fruit trees.

2. To observe and discover the physiological processes which occur within the plant

tissues.

3. To study the external (environmental) factors that surround the fruit trees and how

they can affect their growth and productivity.

4. How one can use the above mentioned points in order to improve the productivity and

the fruit quality of the present orchards, and to put such points in our consideration

for future use.

The nutritional value of fruits

Fruit trees have been cultivated from prehistoric time for human diet. The fruit contains

various chemical substances which provide body with the energy needed to do work, in

addition to those required to build cells, tissues, organs and the whole body as well. Some

examples:

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1. Date fruits: are considered long time ago as a complete diet for the Arabs in many

countries. The fruit contains a considerable amount of sugars, certain amount of

vitamins and certain minerals that are very necessary for both teeth and bone strength.

2. Pomegranates: are used in many medical purposes, fruit rind is used medicinally to

control diarrhea and also for dying and tanning, arils are used for flavoring, making

juice and fruit salad, the arils are rich in vitamins, minerals, pigments and nutritional

compounds.

3. Citrus fruits (oranges, lemon, lime, mandarin…etc): can be eaten fresh, making

jams, jelly, fresh juice… the peel is considered as a source of pectin and essential oil

used in flavoring, making some perfumes and cosmetics. Essential oils may also be

obtained from flowers and leaves.

4. Guava fruits: contain (2-5) times Vit.C content of fresh orange juice. In some

countries, leaves are used medicinally for diarrhea and also for dying and tainning.

5. Mango: is an important source of Vit.A, fair in Vit.B and with varying quantities of

Vit.C.

6. Papaya fruits: are rich in Vit.A, and have some Vit.C. Leaves, as well as young fruits

are usually used to tenderize meat because they have latex that contains the enzyme

Papain which has protein –digesting properties.

7. Avocados: have the highest energy value of any fruit. The pulp(flesh) is rich in Vit.C

and good in Vit.A & Vit.E and oil .

8. Olives: contain a considerable amount of olive oil, which is a very important

ingredient in the diets of the people who live in the countries neighboring the

Mediterranean basin. The oil plays an important role in lowering blood pressure,

cholesterol and sugar levels in the blood of the human. The fruits are extensively used

for making green and black pickles.

9. Apricots: are rich in Vit.A and Iron, followed by Peaches then Plums.

10. Grapes: grape berries (fruits) are commonly used for fresh consumption, making

raisins, juice and canning, they are rich in minerals specially iron which is necessary

for red blood cells renewing..

11. Nuts (Almonds, Walnuts, Pecans .etc): contain remarkable amounts of proteins and

fats, in addition to some elements such as Iron & Copper which, renew the red blood

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cells. Beside the above benefits, the tree is useful as ornamental plant and as a source

of shade for avenues and gardens. Moreover, the wood can be used in making simple

furniture and can be also as fuel. In addition, the fruits are commonly used for making

soft drinks, jam, jelly, ice-cream…etc.

Morphology of Fruit Tree & its Parts:

Fruit trees are perennial plants (living more than two years) grow year after year, often

taking many years to mature. Unlike annuals and biennials, the perennials do not necessary

die after flowering. Perennials may be: Woody such as Olive, Apricot …etc., or

Herbaceous as Banana & Pineapple.

Most fruit species belong to Dicotyledonous plants; however, few fruits such as Date palm,

Banana & Pineapple belong to Monocotyledonous plants. Also fruit crops fall under one of

the following two groups:

1st: Evergreen fruits:

Trees of this group retain living leaves at all times. They lose their leaves gradually, never all

at one time and form new leaves before the old ones are lost. They can grow and thrive well

in tropical, subtropical and warm temperate regions. Examples: Olive, Date palm, Banana,

Mango, Citrus fruits (Orange, Sour orange, Lime, Mandarin, Grapefruit…etc.) … and many

other fruits.

2nd :Deciduous fruits :

The trees are leafless during a portion of the year (usually winter) such a habit is often

associated with temperate regions. However, some deciduous fruits as Grape, Fig,

Pomegranate and Persimmon can thrive well in warm temperate regions. Examples : Grapes,

Figs, Apples, Pears, Peaches, Apricots, Almonds, Walnuts, Plums…etc.

Parts of fruit tree

A tree or a vine is made up of two parts:

1. The subterranean (underground) part or Roots (Root system).

2. The aerial (aboveground) portion or Shoot (Top system) or Stem.

Each thrives in an entirely unique environment and performs vastly functions (Fig.1).

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ROOTS:

Roots unlike shoots because they do not have leaves and nodes with buds or flowers, but

they possess other morphologically distinct features. The Primary or Tap root of a seedling

tree originates from the radical of a seed during germination. The lateral branches of the

primary axis termed Secondary roots.

The Adventitious roots: are those arising from stem, leaf, or other parts than roots.

Functions of roots: Roots serve the various functions of anchorage, support, absorption,

conduction, sometime as organs of vegetative propagation and even for nutritional functions

in special cases.

STEM:

It is the aerial portion of the tree, it possesses nodes and internodes, at which the leaves

occur, and commonly one or more buds are formed in the axil of each leaf.

The following terms are used to refer to the various stem portions of a fruit tree:

Trunk: It is the main axis of the tree from the ground level to the point of branching.

Branches: Are the units or portions of the tree which, carry the lateral growths such

as shoots, twigs or spurs. In case of grapes: branches are termed Arms.

Shoots: A shoot is a new growth (current season’s growth), less than one-year-old. It

is termed shoot also in grapevines.

Twigs: A twig is one-year-old shoot after the leaves fall (during winter); it is termed

Cane in grapevines.

Water sprouts: Rapid growing shoots that arise from latent or adventitious buds on

branches or trunks.

Fruiting spurs: A spur can be defined as a short, woody stem (branch) which is the

principal fruiting area of many fruits. It is characterized by greatly shortened

internodes.

Leaves: The primary function of leaf is to synthesize food for the plant by the

complex process of photosynthesis. It also plays an important role in respiration and

transpiration. Therefore, leaves should be protected against any damages that can

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occur by fungi or insects. Also, removing or separating leaves away from the tree for

cooking purposes –as in case of Grapevines (stuffed leaves) - should be avoided.

Fig. 1

Buds: A bud may be defined as an incipient or unelongated branch. It carries all the

vegetative as well as the fruiting characteristics of the plants. Buds are usually borne

either terminally at the tip of the branch or laterally at the nodes in the axil of each

leaf. There are two types of buds:

1st: Leaf (Vegetative) Bud :

It is known as vegetative bud because when it opens, it gives rise to a shoot (leaves only

with no flowers).

2nd: Flower (Fruit) Bud :

When it opens, it gives either flowers alone or flowers and leaves, therefore, flower buds

are further classified into.

Simple flower buds:

If it posses only flowers. Examples:

Simple flower buds borne laterally, found in: Apricot, Almonds, Cherries, Plums and Peaches.

Simple flower buds borne terminally occurred in: Loquat, Mangoes and Avocados.

1. Mixed flower buds:

If it possesses both leaves & flowers. Exemples: Apples, Pears, Quinces and Grapes.

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Compound bud : In the Grapevine, a group of three buds is often formed within one large

bud or “eye”. This is termed a compound bud. The central one forms the main branch, or

cane, and the two lateral (secondary) ones are small and usually fall soon after growth starts.

If, however, the primary (central) bud dies by any causes, a secondary bud grows to replace

the died ones (Fig.2).

How one can differentiate between vegetative & flower buds?

For the deciduous fruits, it is possible to distinguish between flowering and vegetative buds

using the external feature. The flower bud is large with a swollen apex, whereas, the

vegetative one is smaller with a pointed tip. As for the evergreen fruits, it is difficult to use

the external appearance to differentiate between the two types of buds; however, this can be

done when thin sections of those buds are microscopically examined, (Fig.3)

Fig. 2

Fig. 3

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Fruiting habits of different fruit species

In its largest sense, fruiting habit means: where the flowering (fruiting) buds are located on

the tree? Do they appear on shoots, twigs, spurs…etc., because fruiting habits vary from one

fruit species to another? This point is of a great importance for the growers to know…why?

The answer is: In each dormant season (winter), especially with the deciduous fruits, pruning

should be done. And pruning means: The removal (cutting back) of some wood (shoots,

twigs, laterals, spurs…etc.) away from the tree; so that the grower should know where the

flowering buds of the variety that he grows in his orchards are located, otherwise, he will

destroy the yield (the crop). Now let’s review the flowering habits of some fruits species.

1st Evergreen Fruits:

Citrus spp.: They are mixed flower buds. Flower buds are borne laterally on the

previous growing season’s wood (shoot). During the following growing season, such

buds open to give new growths. Some of them carry flowers in a group or a cluster;

this cluster is termed inflorescence and because it doesn’t carry leaves, it is called

Leafless inflorescence. But when the inflorescence carries leaves and flowers, it is

called Leafy inflorescence.

Loquat, Mangoes and Avocados: The flower buds appear terminally on one-year-old

shoots or less.

Olives: The flowers are associated together in a cluster (inflorescence) which, is

borne in the axil of a leaf. This means that the inflorescence is borne laterally on one-

year-old shoots.

Guava: The flower buds are borne laterally in the axils of the leaves on the new

growth (mixed flower buds).

Papaya: The flower buds appear laterally in the axils of the upper leaves on the stem

(trunk).

Date palm: Date palm is a dioecious plant, i.e. the female flowers are borne on a

plant, while the male flowers appear on a separate tree. A group of flowers appear on

a separate tree. A group of flowers (either male or female flowers) is enclosed in a

“spathe”. Those spathes are laterally in the axils of the leaves.

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2nd Deciduous Fruits:

Apples & Pears: Most of the flower buds are borne terminally on fruiting spurs, a

few fruits, however, can appear either terminally or laterally on twigs (Fig.4).

Quinces: The flower bud when opens, it gives a short vegetative growth that carries

the flowers at its apex.

Apricots, Almonds, Cherries & Plums: The flower buds appear laterally on fruiting

spurs.

Peaches: Laterally on twigs. The buds are borne singly or in particular

combinations as: F, L, FL, FLF, FF, FFF, and LLF. (Fig.5am b, c).

Pomegranates: Laterally on mature wood not less than two-years-old.

Walnuts & Pecans: Female flower buds are borne terminally on twigs; male flower

buds appear laterally on the same twigs. (Fig5-d).

Grapes: The mixed, compound flower buds appear laterally on canes.

Fig. 4

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►Penologists were aware that the position of the flowering buds on the canes determined the

training system that can be employed for a given variety. For those varieties that carry their

flowering buds “eyes” near the base of the Cane, Spur-pruning system is recommended; in

such a case, dormant canes are headed back (cut back) to 2 or 3 bud spurs. This type of

pruning is used with Head-training-spur-pruning and Cordon systems. The most well known

varieties that are trained by this method, Muscat of Alexandria, Italia & Rosaki. Certain

other varieties such as Thompson Seedless, Gharibi & Romi White carry their flowering

buds “eyes” near the free end of the Cane (at about nine nodes from the base ), therefore, the

most suitable system that can be used is Head-training-cane-pruning.

Factors affecting flower bud formation

There are many factors that affect the flower bud formation of the different fruit species,

some of them are internal (physiological) and the other are external (environmental).

First: Internal or Physiological Factors:

A – C/N ratio:

Observation that vigorous trees tend to produce few flowers led Kraus & Krybill (1918) to

investigate the role of Nitrogen in flower formation and fruit set. Their data revealed that

high Nitrogen and low Carbohydrates contents in Tomato led to poor fruit set. In 1947,

Gourley & Howlett developed a model for apple tree similar to that for tomato. They

classified the Apple tree in four groups or classes as follows (Fig.6).

Class I:

Apple tree included in this class, are carbohydrate deficient and weakly vegetative, although

Nitrogen is adequate, so they will not form flowers. Carbohydrate deficiency is due to low

rate of photosynthesis caused by shading, defoliation or other factors.

Class II:

Tees of this class are slightly carbohydrate-deficient and moderately vigorous from heavy

Nitrogen fertilization, but they do not flower. This deficiency is not due to failure of

carbohydrate synthesis, but to the rapid carbohydrate utilization in the formation of organic

nitrogenous compounds (in presence of abundant supply of inorganic Nitrogen). Trees of this

class are either young or severely pruned.

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Fig. 5-a

5-b 5-c

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Fig. 5 –d; 1 –female flowering bud, 2- male inflorescence.

Class III:

The trees contain adequate and balanced Nitrogen and carbohydrate supplies, therefore. They

produce abundant flowers and set crops.

Class IV:

The trees lack Nitrogen produce few flowers that rarely set fruits. Those trees do not receive

adequate Nitrogen and are not pruned (neglected orchards).

It’s obvious that the tree can be shifted from one class to another by adjusting the severity of

pruning and the amount of the applied fertilizers.

B – Florigens:

Florigens are flowering–producing hormones which are manufactured in the young active

leaves, then translocate to the buds, inducing them to initiate flowers. Therefore, any damage

could occur to the leaves by any cause prevents the hormone from reaching the bud.

Second: Environmental Factors

1. Light: Light of high intensity favors flower formation in fruit trees. Therefore,

lowering light intensity by shading or overcrowding reduce flower formation. It was

noticed that, the light intensity in interior of a dense unpruned tree is much lower than

that at its periphery. In such a case, flower formation will confine only at the

periphery rather than at its interior. To overcome this problem, it is necessary to

remove (prune) some interior branches to allow the penetration of light.

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Fig.6

2. Girdling (Scoring): Girdling or ringing involves the removal of a ring of bark

including phloem from the trunk or branches of a tree. This operation temporarily

restricts movement of photosynthates from leaves to roots and results in an

accumulation of carbohydrates and hormones above the girdle which stimulates

flower bud formation. This operation is not recommended for Stone fruits, since it

damages the tree. Also, it was noticed that weak trees do not respond to girdling. For

best results, girdling should be done 3 weeks before flowering. (Fig.7).

3. Dwarfing Rootstocks: Cultivars grafted onto dwarfing rootstocks, usually come into

flowering at an earlier age than those grafted on standard seedlings. The overall result

of such a scion-rootstock combination is that both top and roots do not grow

vigorously, (Fig.8).Hence, assimilates are directed toward flower bud formation, fruit

development, and the formation of spurs rather than for long vegetative shoots.

Examples: Citrus grafted on trifoliate orange, Apples grafted on Malling 9 and Pears

grafted onto Quince.

4. Root Pruning: Sever injury to the roots of fruit tree, increases flower bud formation.

This is because root pruning reduces the entrance of water and nutrients, thus

retarding the growth of the top and favors flower bud formation. This operation has

long been employed to induce flowering in vigorous Lime trees. However, root

pruning can cause a lot of injuries to fruit trees.

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Fig.7

5. Defloration: Removal of some flowers from the tree, will increase the differentiation

of the floral primordia for the succeeding year, and consequently will increase the

flower bud formation of that year.

6. Defoliation: Removal of a leaf subtending a bud prevents the differentiation of

flowers in that bud, even though other leaves are present at adjacent nodes. Therefore,

any defoliation occurring as a result of disease or injury of any sort may either

prevent or greatly reduce flower bud formation.

7. Fruit Thinning: Trees of certain fruit varieties such as Apple, Olive, Date palm,

Baladi Mandarin, etc., tend to bear a heavy crop (on-year) and carry a little or no

crop the following year (off-year).

This phenomenon is known as “Alternate bearing". Removing some fruits when they

are still young during the on-year (especially with the heavy bearing varieties such as

Grapes and Peaches) favors flower bud formation the next year. This effect can be

attributed to the fact that, removing some fruits of the on-year crop preserves the

stored food in the tree tissues for flower bud formation and consequently increases

the yield (crop) of the following year (off-year). By this operation the yield can be

regulated year after year.

8. Water Supply: Appropriate reduction of soil moisture stimulates flower bud

formation the next year. This can be explained according to the fact that lack of water

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reduces the vegetative growth of a tree, and directing the preserved food stuff toward

flower bud formation. Sever water deficiency, however, will reduce flower bud

formation.

9. Nitrogen Fertilization: Applying concentrated nitrogen fertilizers to fruit trees will

accelerate the growth of shoots, leaves, stems, and spurs which: consume the stored

carbohydrates and consequently reduce flower bud formation. Light or moderate

application tends to increase flower bud formation, however.

10. Pruning: Pruning young non bearing trees either delays or reduces flower bud

formation. Light or moderate pruning of heavy bearing trees tends to increase flower

bud formation. This favorable effect on bearing trees can be assigned to a number of

factors, the more important being: increases light, increases leaf size, due to the

release of additional water and nitrogen, and a reduction of the exhaustive effect of

fruit production.

Fig. 8

11. Spray Materials: Certain spray materials such as Liquid-Lime-Sulfur solution,

summer oils, mineral oils, etc., have reduced the rate of photosynthesis and causes

injuries to the leaves, thus reduce flower bud formation.

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12. Growth Retardants: Growth-retarding substances such as Cycocel and

Diaminozide were developed to control plant size, but they were soon found to

promote flower bud formation. Examples: Bloom density on treated Apple and

Cherry trees were greater than that on untreated trees.

13. Branch Positioning: Bending branches toward the horizontal inhibits shoot

elongation and promotes flowering.

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principles of fruit production (pomology 16201) chapter 1...

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