Physiology of Pepper

ByKwesiga Julius MSc.2010/HD02/3432U

Outline

• Introduction• Seed germination• Vegetable growth• Induction of flowering• Fruit set• Fruit growth and maturation• Physiological Disorders • Conclusion

Introduction

Uganda’s Horticulture sector is one of the fastest growing sectors in Uganda’s economy

Its one of Uganda’s Strategic Exports sector employing a large

number of people & worth USD $ 35 million annually Its importance in Uganda's economy is due to its contribution

to foreign exchange earnings, employment opportunities, rural development and food and nutritional security.

Hot pepper one of the export components is grown in the districts of Luwero, Mpigi, Mukono, Wakiso, Kasese, Lira, Jinja and Hoima

Introduction…… Hot pepper export volumes have increased since 1991 to

date and is expected to continue increasing because of demand.

Its wholesale price of USD 3.75 per kilogram .

Locally, the smallholders sell their hot pepper to middlemen in specified cartons which go for between 2500 - 9000 UgShs depending on demand.

In this presentation allow me focus on the physiology of this crop.

Introduction……

• Kingdom :  Plantae - Plants Subkingdom :  Tracheobionta - Vascular plants 

• Superdivision :  Spermatophyta - Seed plants Division :  Magnoliophyta - Flowering plants Class :  Magnoliopsida - Dicotyledons (two seed leaves)Subclass :  Asteridae 

• Order :  Solanales 

 Family :  Solanaceae - Nightshade or Potato family   Genus :  Capsicum L. - peppers     

Introduction……

  Species :  Capsicum annuum - -

Bell, cayenne, and most cultivated varieties of chiles Capsicum baccatum - -

aji pepper or Peruvian hot pepper, no varieties domestically grown

Capsicum chinense  - -

Includes Habanero, Tabasco and Squash peppersCapsicum pubescens - -

Includes Rocoto, no varieties domestically grown

Introduction

• Capsicum pepper are herbaceous, frost-sensitive plants that in temperate areas.

• Annual in growth duration, but areas may continue to grow and reproduce yield over several years.

• They are the source of capsaicin, the most most commonly used spice in the world. Other uses include; green or mature fruits for salads

• As cooked or raw vegetables, • red food colouring, • As medicine

Seed germination• Germination and emergence of pepper is slow at room

temperature and further delayed by cooler conditions.

• At 25oC, pepper requires 3.5 days for radicle emergence, while at 15oC, 9 days. Emergence from 1.2cm soil depth takes 8-9 days at temperature from 25-35oC.

• Removal of the testa makes little difference in germination rate,

• Removing the endosperm which the radicle has to penetrate halfs the germination time at 25oC and reduces it from 9 to 3.4 days at the 15oC.

Seed germination• It thus appears that the endosperm constitutes the

principle barrier to radicle emergence.

• The growth promoter gibberllic acid may increase the speed of radicle penetration.

• It is possible that GA stimulates enzyme activity that enhances endosperm breakdown in the area near the radicle tip.

• Germination of pepper seeds may be preceded by a period of dormancy.

Vegetative growth

• Pepper also has a relatively slower seedling growth rate than some other vegetable crops.

• Comparative growth analysis of tomato, cucumber and pepper indicates that pepper has a 25% lower relative growth rate.

• Pepper seedlings have significantly thinker leaves (higher

specific leaf weight) than the other two species.

Vegetative growth

• It is possible to reduce leaf thickness and increase the proportion of leaf area to total plant mass (leaf area ratio) by reducing incident light.

• These changes occur at the expense of the plant growth

rate, however, and may thus be counterproductive.

• Use of light shade (25-50%) during seedling growth has been advocated to increase yield of pepper in a tropical environment.

Vegetative growth

• The rate of plant growth is also strongly influenced by the air temperature.

• This affects both the rate of DM prodn and the partitioning of that DM into leaf tissue.

• Pepper growth in the vegetative stage has been found to be greatest at 25-27oC day and 18-20 oC night temperature.

Vegetative growth

• In the field direct seeded peppers grown in a deep soil develop several prominent roots that may reach a depth of 3m.

• When transplanted, root growth is shallower and more branched, with 80% of the active root system found in the upper 75cm of soil.

• Root growth is proportional to shoot growth in the vegetative period in pepper.

Vegetative growth

• Root growth and distribution are significantly influenced;• Soil management,• Cultivation, • Extent and distribution of irrigation water.

• Root distribution is also significantly affected;• Root structure and density, • Polyethylene mulch, a common practice in pepper

production.

Induction of flowering • The production of flower

primordial appears to be little influenced by daylight.

• Under most growing conditions, many pepper cultivars produce a terminal flower after 8-10 leaves on the main stem.

• Typically 2 or 3 branches arise at the apical meristem, which again terminate in flower after producing one node.

Induction of flowering

• In the field the same pattern is then repeated for about 5 nodes, depending on the length of the growing season.

• The number of nodes formed before flowers are initiated appears to be little influenced by environmental factors.

• Main stem leaf number showed little variation with changes in photoperiod, except when short days were combined with warm nights, in which case flower initiation was delayed by one node.

Pepper flower

A fully-opened flower, and an already-pollinated fruit.

Fruit set

• Flower of pepper are generally considered to be self-pollinated, although unlike tomato, the anthers and stigma often do not touch each other.

• On many cultivars, flowers are held horizontally or pendent, so that pollen can fall onto the stigmatic surface.

• Presumably, in the field insects’ help to transfer pollen and increase fruit set, on average of 14% out crossing among tester lines inter planted in chilli pepper fields.

Fruit set

• Under the windstill conditions of glass houses, the introduction of bees during flowering increased the seed set and fruit size of the fruits produced.

• On the day of anthesis, the pepper flower begins to open by dawn, and most new flowers are open by 0800 hours.

• Anther dehiscence commonly lags behind the flower opening by 1 or 2h, but in some cultivars has been reported to be questioned.

Fruit set

• A similarly long stigma receptively period was found. The evaluation of pollen viability has been hampered by the lack of a reliable in vitro germination medium.

• Recently, it was found that a liquid medium containing sucrose, boric acid and calcium chloride improved pollen germination and pollen tube growth over media previously used.

• There is a considerable lag in seed set after pollen has been placed on the stigma. Fertilization occurred 42h after pollination for plants grown at 27/21oC.

Fruit set

• Pepper has the capacity to set fruit parthenocarpically, especially under low temperature conditions.

• Failure of seed set is at least partly due to formation of abnormal and non-viable pollen.

• Male sterility is controlled by both nucleic and cytoplasmic genes. In both types of male sterility, anthers stayed small and shrunken, and were blue-violet in colour, with little or no viable pollen

Fruit growth and maturation

• The process of fruit growth begins with the formation of the ovary during the early stages of flower differentiation.

• In the period before anthesis of the flower, the basic structure of the ovary is determined, including the number of carpels to be found in the mature fruit.

• Cell division predominates during this stage, followed by cell enlargement after flowering .

Fruit growth and maturation

• Some cell division activity is however, maintained into later stages of fruit growth in long-fruited pepper types, especially at the basal part of fruit.

• Pepper fruit formation differs from that of tomato and squash in that the shape of the ovary at anthesis gives less indication of final fruit shape.

• Changes in cell shape and the plane and amount of cell division thus influence profoundly final fruit shape.

Fruit growth and maturation

• The temperature at which the plant is growing during this pre-anthesis period can also influence fruit shape.

• Subjection pepper seedlings to 35oC from the time the third leaf was longer than 1 cm resulted in a significant increase in fruit locule number, with increasing fruit size.

• If plants are grown at low night temperature (8-10oC) before flowering the ovary tends to be larger and broader than that of plants grown at higher (18-20oC) temperatures.

Fruit growth and maturation

• The increased ovary size of such cool temperature grown plants does not result in bigger fruits at maturity, however, even if normal pollen is used to ensure seed set.

• small, seedless fruit are often the result of growing pepper plants in cool conditions.

• Condition which negatively influence overall plant growth can also reduce final fruit size

Fruit growth and maturation

• As fruit number per plant increase, the size of individual fruit set allows the plant to develop the retained fruit to large size.

• Unfortunately, the selection of pepper genotypes with large fruits has probably resulted in cultivars that are very susceptible to flower and flower bud abscission.

Pepper Paprik

Sweet paperPepper Salsa

Hot pepper

Habanero

Conclusion

• The physiology of the pepper plant reveals it to be a rather demanding crop.

• Once the fruits are growing actively, the plants very efficiently partition assimilates to both the fruits and to maintenance of the vegetative organs.

• The plant typically retain much of the leaf area in the late reproductive period, and if weather conditions permit, will continue to produce additional flushes of reproductive organs.

Thank you for the attention

Am off to the market

Physiological disorders of

Physiological Disorders

• Blossom-End Rot• Fruit cracks• Pepper Stippling• Sunscald• Poor Color Development• Abnormal fruit shape• Nutrient and Other Disorders

Blossom-End Rot

• A dark brown to black necrotic region on the blossom end of developing fruit.

• This disorder is associated with calcium deficiency.

Fruit cracks

A very fine, superficial cracks on the surface of the pepper fruit which gives a rough texture to the fruit . The developments of these cracks are associated with sudden changes in the growth rate of the individual fruit.

Pepper Stippling

Associated with Ca deficiency.Small (0.25 inch) spots occur inside the fruit wall as the pepper reaches maturity. These spots are brown or black and result in green or yellow spots occurring on the fruit surface.

Potassium deficiency may also play a role in this disorder.

Sunscald

• Occurs when ripening fruit is not adequately shaded by leaf cover.

• Large sections of the exposed fruit can develop gray or brown paper-thin areas. These areas render the fruit unsalable.

• varieties that produce sufficient leaf canopy.

Poor Color Development

• Occurs when peppers don’t receive sufficient light into the canopy.

• This can be a particular problem when peppers are grown to full maturity and allowed to develop to colors beyond the initial green.

Abnormal fruit shape

• The development of misshapen fruit is generally associated with sub-optimal growing conditions at flowering and pollination which result in poor flower development or poor pollination.

Nutrient and Other Disorders

• Nutrient disorders beyond blossom-end rot can occur in peppers if fertilization is inadequate.

• Low soil pH can result in stunted plants that exhibit magnesium deficiency. Low pH can also contribute to toxicity from aluminum.

• Toxicities can also occur due to applications of certain fungicides, particularly copper based materials, or due to non-target herbicide use that may be difficult to assess.

Conclusion

Physiological disorders are part of the physiology of pepper will hence affect the marketability and nutritional quality of the pepper.

Reason why attention should be placed on how to over come them.

Once this is taken care of then pepper yield s will hence forth be high in relation to the amount planted

Thank you