Reproduction

Like all plants, dill has an alternation of generations, and its dominant phase is the diploid sporophyte (the plant that you usually see). Dill, being an angiosperm, has unique and specific means of reproduction. Angiosperms are unique in that they have seed coverings, which are very important because they provide protection and nutrition for the embryo.

                                                      Dill seeds are about 1mm wide.
                                                This is what dill seeds look like close up!
                                       

First let’s get familiar with a couple structures that are involved in reproduction of dill. At the bases of dill’s flowers are ovaries, which contain ovules. The ovules contain megaspores. (Megaspores are analogous to egg cells in humans.) Dill also has anthers that stick off the flower and produce microspores which become grains of pollen. (These are analogous to sperm cells in humans.) The stigma is a structure at the top of the style (a long structure that resides in the middle of the flower) that functions in “collecting” the pollen via pollinators. The pollen tube, located inside the style, functions in carrying the pollen to the ovule inside the ovary.

   

Now let’s talk about the process of reproduction in dill. The megaspores and microspores are produced through meiosis. The microspores then undergo mitosis to form grains of pollen, which are discharged at the top of the anthers. This is where pollinators such as bees, butterflies, and moths come in. When these pollinators land on the flowers of the dill plant to obtain food, they end up collecting grains of pollen on their bodies. They then fly around to other flowers and deposit the pollen on top of the stigma of another flower on another plant. This creates cross pollination. Dill can also pollinate itself; however, this is not the most advantageous way to reproduce because it does not create genetic variability, so cross pollination is the preferred method.
                                 
The grains of pollen move through the pollen tube and are deposited inside an ovule containing megaspores. The megaspores are fertilized by the pollen that contains microspores. In angiosperms, however, a special event called double fertilization occurs. Not only is a zygote (2n) produced, but an endosperm (3n) is produced as well. Endosperms are extremely important because they provide nutrients for the seed when it comes time to grow; this is an important adaptation as seeds begin in the ground where they do not have access to sunlight. Also, the seed contains 2 cotyledons, which will become the first two leaves of the plant and produce the first energy for the plant to grow big and tall.

                         
There are several organisms that help aid in the reproduction of dill. To learn about dill's interactions with other organisms, click here!


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