Flowers - Structure And Function (1964)

a great variety of flower colors and forms becomes apparent in the spring when flowering plants both cultivated and wild reach the peak of their blooming although There is almost endless Variety in the shapes and colors of flowers the structure of every flower is intricately related to its function which is pollination flowers of the mustard plant are pollinated by bees insects are the Agents of pollination for many kinds of flowers pollination the transfer of pollen from stamens to pistol involves the reproductive parts of a flower pollen is produced by the male parts the stamens in a mustard flower there are six stamens four long and Too Short in the center is the female organ the pistol which will produce seeds in the ovary at the base of the pistol at the base of the petals are glands which secrete the nectar the nectar attracts bees which thus become the agents for cross-pollination of the flowers this is an example of both insect and plant adaptations certain flowers have very highly specialized adaptations for insect pollination let's look at the structure of the common vetch a member of the legume family insects generally land on the lower most petals or Keel of the flower with a match we depress the keel and pollen is released from the anthers when a bee alights on the Keel of the flower her weight causes the pollen to be discharged her body becomes covered with pollen which will be rubbed on the stigma of the next flower the bee visits another flower admirably adapted to pollination by bees is the iris to get the nectar the bee has to crawl deep into the flower the anthers dust the bees back with pollen the pollen producing anther is at the tip of the stamen which is curved the anther presses downward on the back of the bee when the insect enters the next flower the pollen is deposited on the petal-like stigmas this particular arrangement of anther and stigma tends to prevent self-pollination azaleas are pollinated by a variety of insects although the flowers vary in size and color depending on species all azaleas have the same basic structure the five petals are fused at the base to form a United Kerala the Azalea has five stamens the pistol is long and slender a flower which contains both stamens and Pistol is bisexual and is termed a perfect flower some flowers such as those of the watermelon are unisexual this is a male flower of the watermelon it is a stamina flower that is it has only stamens pollen from the anthers on the stamens may be carried by a butterfly to a female flower this is a pistolate flower having only a pistol bearing the stigmas the squash belonging to the same family as the watermelon also has unisexual flowers after pollination the ovary below the Kerala begins to develop into the squash fruit the Kerala gradually Withers away as the squash develops one of the largest families of flowers are the Composites which include the dandelion what appears to be a single flower is actually a flower ahead composed of many separate flowers supported on a common stock the flower head is at the left two individual flowers at the right the forked part is the branched style which supports the stigma surrounding the base of the style are the anthers the ovary which will mature to form the single seeded fruit can be seen below the Downy hairs or Pappas although it may appear that the flower has a single petal there are really five petals which have fused to form the strap-shaped Corolla the lines of fusion of the five petals can be seen on very close examination of the flower so although very small the dandelion has all parts and is both a perfect and a complete flower although the ovary of the dandelion May develop a seed without pollination the flowers are also pollinated by insects after maturing each ovary of the dandelion contains a single seed in time lapse we see how the white hairs or Papas spread out the seeds with their fragile hairs are easily carried by the wind if a seed lands in a suitable place it will germinate this reproductive function is the principal work of flowers the rice plant a grass has small rather inconspicuous flowers which generally do not attract insects but the wind carries pollen from the exposed stamens to the bushy stigmas many kinds of pollen are borne by the wind the pollen grains are microscopic in size each kind of flower produces its particular kind of pollen we've seen that pollen may be carried by the wind and by insects such as butterflies and bees bees collect pollen as well as nectar for food the bee's body is well adapted for carrying large amounts of pollen and behind legs are so-called pollen baskets in which the pollen is collected many bristles on the hind legs help support the massive pollen the microscopic grains of pollen adhere to the stigma which may have hook-like hairs or may have a sticky liquid which holds the pollen when the pollen reaches the surface of a stigma each pollen grain extends a pollen tube seen here highly magnified and in time lapse photography each pollen grain puts out a pollen tube which conveys the sperms to the egg a tube grows down into the pistol when it reaches an ovule fertilization takes place and the ovule develops into a seed in reviewing flowering plants remember that the principal function of the flower is reproduction slow motion shows the opening of the petals and sepals a bisexual flower such as this Lily contains male parts the stamens bearing the anthers laden with pollen and a female part the pistol bearing the stigma the transfer of pollen from the anthers to the stigma affects fertilization of the ovary no matter what their species or habitat the structure and function of their flowers enable these plants to reproduce their own kind [Music]