ZOOPHILY & ENTOMOPHILY

STD-12      UNIT-6     CHA-2

REPRODUCTION IN FLOWERING PLANT

ZOOPHILY & ENTOMOPHILY

ZOOPHILY

• Zoophily ( Gk . zoon animal , philein- to love ) . 

• It is pollination through the agency of animals . 
• The most common type of animal pollinators are insects . 
• Others are birds , bats , snails , human beings , etc. 
• Some primates ( e.g. , Lemurs ) , arboreal rodents and reptiles ( Gecko Lizard , Garden Lizard ) have also been found to accomplish pollination inadvertantly Zoophilous flowers are often adapted to be pollinated by particular type of animals .
• Bees and butterflies pollinate the maximum number of flowering plants . 
• The two common families pollinated by them are Asteraceae and Lamiaceae.

• Entomophily ( Gk . entomon insect , philein to love : Insect Pollination ) . 

• It is the most common type of zoophily in which the pollen grains of ripe anthers of one flower are transferred to a mature stigma of another flower through the agency of insects like moths , butterflies , wasps , bees , beetles , etc. 
• The insects visit the flowers for nectar , edible pollen grains or shelter . 
• Bees do pollination in nearly 80 % of the flowers . 
• They obtain both nectar and pollen grains from the flowers . 
• Bees have pollen baskets for collecting pollen .

• Characteristics of Entomophilous Flowers

• Entomophilous flowers are coloured for attracting pollinating insects . 
• Moths visit whitish flowers , butterflies and wasps reddish flowers , bees are attracted towards blue , purple - violet and yellow flowers . 
• Bees use ultraviolet radiations for observation . 
• Red appears black in ultraviolet radiations . Therefore , bees seldom visit red flowers . 

• The various traits of ento mophilous flowers are : 

• They are showy or brightly coloured . 
• The small flowers become conspicuous by their grouping , e.g. , head in Sunflower . 
• Where petals are not conspicuous , other parts become showy , e.g. , bracts in Bou gainvillea , leaves in Euphorbia pulcherrima , spathes in aroids , one sepal in Mussaenda , stamens in Mimosa , Acacia , etc.
• Most insect pollinated flowers have a landing platform . 
• Some flowers have structural peculiarities to get pollinated by particular types of insects , e.g. , opening of bilabiate personate flowers of Snapdragon ( Antirrhinum ) by particular weight by the pollinator or depth of the corolla tube for different tongued insects . 
• In many cases special markings occur on the petals for guiding the insect to nectar glands . They are called honey or nectar guides ( e.g. , Viola ) . The latter often reflect ultra violet radiations for recognition by bees . 
• The flowers produce an odour which may be pleasant ( e.g.  Jasmine ) or foul ( e . g .Aristolochia , Arum , Rafflesia ) . Foul smell attracts flies and beetles . Odour of Rafflesia attracts Carrion flies ( Fly trap mechanism ) .
• Nectar is secreted for feeding the visiting insects . Nectar glands are placed in such a position that an insect must touch both the anthers and the stigmas .
• Edible pollens are produced by Rosa , Clematis , Magnolia , etc. 
• Usually stamens are inserted except when they are specialized for attracting insects ( e.g. , Mimosa ) . 
• The pollen grains are spiny , heavy and surrounded by a yellow oily sticky substance called pollenkit .
• Stigmas are often inserted and sticky .
• Pollinia of Calotropis and related plants cannot be transferred to the stigmatic surface without the help of an insect .
• Some flowers provide safe place to insects for laying eggs , e.g. , Yucca , Amorphophallus . The tallest flower belongs to Amorphophallus ( six feet tall ) .

• Special Adaptations in Entomophilous Flowers

• Some plants have special adaptations for the insect visitor to help in cross pollination . In Salvia a turn - pipe or lever - mechanism operates to promote cross pollination . Salvia  is pollinated by bees It has protandrous flowers with blipped corolla . The lower lip functions as a landing platform for the insect . Each stamen has long connective which bears a fertile anther lobe at the upper end and sterile plate - like anther lobe at the lower end . The two sterile anther plates lie side by side and block the path of the insect . As the insect moves in ward a young flower in search of nectar , its head pushes the sterile anther plates and forces the fertile anther lobes to strike against its back . In older flower the style brings the stigma in such a position that it brushes against the back of the insect and collects pollen grains brought by the insect from a young flower . 
• There is a mutual dependence between Fig and its pollinating agent . female gall wasp Blastophaga . Hypanthodia of the plant possess gall flowers for feeding the grubs of the wasp . The early life of wasp is passed inside the hypanthodium . The young wasp coming out of the hypanthodium having mature male flowers drops the pollen inside another hypanthodium having mature female flowers ( trap door mechanism ) . It deposits its eggs in gall flowers . 
• Prob ( = Tageticula ) yuccasella is a moth which deposits its eges in the ovary of Yucca flower . Simultaneously , it collects pollen and deposits the same in the hollow of stigma to effect pollination . 
• In several species of the orchid like Ophrys speculum the shape , colour , markings and odour of the flowers is like the female moth Colpa . The Ophrys employs sexual deceit to get pollination done by the Colpa . The male moth matures earlier than the female . It mistakes the Ophrys flower for female moth and tries to copulate ( pseudocopulation ) . In this attempt , it pollinates the flowers .

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