PINEAPPLE TREE

PINEAPPLE TREE

Botanical and physiological adaptations

Pineapple is a tropical plant and grows best in a moderately warm climate (16° to 33°C) with low, but regular rainfall. It is estimated that Smooth Cayenne requires only 50mm of rainfall per month for optimum growth. It has some important limitations:  It cannot tolerate frost 

• It is intolerant of high temperatures (in excess of 40°C), and sunburn damage to plants and fruit can be severe.
• It has a fragile root system that needs well-drained conditions Pineapple has several special characteristics that allow it to survive and thrive under low rainfall conditions: 
• Leaf shape and orientation that maximises capture of moisture and sunlight most efficiently. 
• The large cups formed where the leaves attach to the stump are effective reservoirs for nutrient solutions and water. 
• The ability to absorb nutrients through axillary roots in the leaf bases, and directly through the leaf surfaces especially the basal white tissue.
• Low numbers of stomata, and leaves that are insulated to reduce water loss.
• Water storage tissue that can make up to half the leaf thickness, and is used during periods of low rainfall to help maintain growth. 
• A specialised metabolic system (CAM) for capturing carbon dioxide at night for use during the day that greatly reduces water loss. 

Flowering

Pineapple is an indeterminate flowering plant which means it has no specific flowering trigger like day/night length, for example. Natural initiation of mature plants (12+ months old) for summer harvest is strong because initiation takes place in winter. Natural initiation for winter harvest - while present - is much weaker because initiation occurs in warmer months when vegetative growth is strong.

Because of this "random" nature of flowering, fruiting can be spread out and require many harvest rounds to complete a crop. Good crop control requires careful planning. Uniform planting material type and size (tops, slips and suckers mature at different times), a uniform strike and intelligent use and timing of flower induction treatments will result in more uniform fruiting, and allow for controlled ripening.

Fruit

The pineapple is technically called a Sorosis – "a fusing of many fruits together to form one unit". Each "eye" (fruitlet) is a complete fruit. Flowering starts at the bottom of the Sorosis and continues up as a spiral to the last eye. When the formation of fruit lets stops, the growing point reverts to a vegetative state and the top (crown) is formed. A good induction will ensure a large number of fruitless are formed which, with good cultural care, will all fill out to give a well-shaped, high-yielding fruit.

Because ripening of the fruits follows the same pattern as flowering, the bottom portion of pineapples is riper, sweeter and has better flavour than the top. Shorter fruit with a little taper (summer plant crop and ratoon fruit) mature more uniformly than larger, tapered autumn to spring plant crop fruit.

Pineapple, like strawberries and citrus fruit, contains no starch reserves so cannot become "sweeter" after harvests like pears, stone fruit, rockmelons and bananas.