horti fruit
Pollination
Definition: Transfer of pollen grains from the anther to the stigmatic surface.
Types of Pollination:
Self Pollination: Pollen from the same flower or plant.
Cross Pollination: Pollen from different flowers or plants, important in horticultural crops for several reasons:
Dioecious crops (e.g., Papaya, Date palm, Nutmeg) need pollen from another plant.
Flower structure peculiarities (e.g. Brinjal, Delicious apple, Vanilla) can necessitate cross-pollination.
Dichogamy (different timing of pollen release and stigma receptivity) affects cross-pollination in crops like Onion, Carrot, and Avocado.
Bisexual flowers may functionally act as unisexual (e.g., Avocado).
Self-incompatibility and self-sterility in certain crops (e.g. Apple, Buckwheat) require cross-pollination.
Methods of Pollen Transfer:
By Insects (Entomophily): Honey bees and other insects.
By Wind (Anemophily): In crops like Sapota, Jack fruit, Aonla, Walnut, and Peanuts.
Bee keeping: Enhances fruit set and yield (e.g., Apple, Cardamom, Coconut). Honey bees can visit 50-100 flowers daily per tree.
Artificial Pollination: Used when self-incompatibility is faced, e.g., in Apple and Pear. Techniques include:
Mentor pollen technique: A mixture of compatible pollen to overcome crossing barriers.
Pioneer pollen technique: Pollination with compatible pollen at two different times.
Hand Pollination: Using brushes to apply pollen or placing bouquets of pollinizers in trees.
Fruit Set
Definition: Initial setting of fruit shortly after blossoming. It is categorized as:
Fruitful: Blossoms that set fruits and carry them to maturity.
Unfruitful/Barren: Inability to set or mature fruits.
Fertility: Capacity to set and mature fruits developing viable seeds.
Infertility/Sterility: Inability to set and mature fruits or viable seeds.
Self Fruitfulness: Ability to mature fruit without pollen from another flower.
Self Fertility: Ability to mature viable seeds without external pollen.
Causes of Unfruitfulness:
Internal Factors:A. Evolutionary tendencies (dioecious vs. monoecious). B. Genetic influences (e.g., hybrid sterility). C. Physiological influences (e.g., slow pollen tube growth, nutritional conditions).
External Factors:
Nutrient supply issues (overfeeding leading to sterility).
Dependency on pollinizers.
Pruning and training practices affecting flower production.
Locality differences in self-sterility.
Seasonal effects on pollination capability.
Temperature's impact on stigmatic fluid for fertilization.
Light's effect on flower development.
Pest and diseases affecting fruit set.
Spraying during blooming can inhibit pollen germination.
Seedlessness in Horticultural Crops
Definition: Often a market preference in recent years.
Parthenocarpy: Development of fruit without fertilization:
Vegetative Parthenocarpy: Fruits develop without pollination (e.g., Banana, Japanese Persimmon).
Stimulative Parthenocarpy: Requires some pollen for development but no fertilization (e.g., Seedless Watermelon).
Steno-spermocarpy: Pollination and fertilization occur, but the embryo aborts (e.g., Thompson Seedless grapes).
Advantages: Higher consumer demand and pricing; resolves issues of unfruitfulness.
Disadvantages: Fruits may be smaller or irregularly shaped.
Induction of Seedlessness:
Use of Growth Regulators: E.g., GA treatment on emasculated flowers to induce seedlessness.
Changing Ploidy Levels: Crossing tetraploid with diploid crops to produce triploid results in seedlessness.
Parthenogenesis: Some fruits develop parthenocarpically yet produce viable seeds (e.g. Mangosteen).
Bearing Habit
Definition: The relative position of fruit development concerning the type of shoot that produces flowers.
Types of Flower Bearing Shoots:
Group 1: Terminally producing inflorescence without leaves (e.g., Mango).
Group 2: Terminally producing leafy shoots with flower clusters (e.g., Apple, Pear).
Group 3: Terminally producing leafy shoots with flowers in leaf axils (e.g., Guava).
Group 4: Laterally producing flowers without leaves (e.g., Citrus, Coconut).
Group 5: Laterally producing leafy shoots with clusters (e.g., Grapes).
Group 6: Laterally producing leafy shoots with flowers in leaf axils (e.g., Fig, Avocado).
Group 7: Both terminally and laterally producing inflorescence (e.g., Walnut).
Group 8: Adventitiously borne on the trunk or old shoots (e.g., Jack, Cocoa).
Fruit Drop
Definition: A natural process where a large number of flowers drop, preventing resource exhaustion.
Stages of Fruit Drop:
First Drop: Shortly after flower opening, includes aborted flowers.
Second Drop: Unfertilized and some fertilized flowers drop; relates to nutritional adjustment.
Third Drop: At marble size; facilitates natural thinning for better fruit size.
Pre-Harvest Drop: Loss before harvesting; causes include:
Mechanical factors like wind and hail.
Climatic factors; high temperature or low humidity can hasten abscission.
Physiological factors related to soil moisture fluctuations.
Nutritional issues (lack of nitrogen can increase shedding).
Cultural practices (deep digging can harm roots).
Pathological causes (diseases can impact fruit set).
Varietal factors can differ within types concerning fruit drop behaviors.
Prevention:Proper cultural practices, timely irrigation and fertilizer application, pest control, and understanding auxin's role in fruit abscission (through plant growth regulators).
Alternate Bearing
Definition: A cycle where fruit trees bear in one year, but fail to flower the next year (common in Mango, Olive, Coffee).
Demerits: Lower average yields; inferior fruit quality; structural damage to branches.
Causes:
Genetic predisposition.
Bearing habits of the tree.
The age of trees.
Nutritional ratios (C/N).
Endogenous hormonal factors affecting growth.