Corn silk and its functions

A corn silk a common species of corn silk, is a shiny,threadlike weak fiber that grows as part of the ear of corn;a cluster or fringe of silky fibers protruding from the tip of the ear of corn.The ears are surrounded by modified leaves called shells.Each individual fiber is an elongated style attached to a separate ovary.The term probably originated sometime between 1850 and 1855.

Development

Each ear of corn forms up to 1000 ovules (potential kernels),each of which produces a bundle of corn silk from its tip,which eventually emerges from the end of the ear.The emergence of at least one silk from a given ear of corn is defined as growth stage R1,and the emergence of silks from 50% of the plants in a cornfield is referred to as "mid silk".Filaments elongate from the basal ovule beginning 10 to 14 days before growth stage R1; this is due to a change in shape of existing cells rather than their duplication.Elongation initially increases at a rate of 1.5 inches per day,but gradually slows as full length is approached.The elongation of the corn silk strands stops after capturing a single pollen or due to silk senescence 10 days after emergence.If the ovules are fertilized successfully,the silks will fall off the ovules after two or three days.Otherwise,the silk will attach indefinitely,and fertilization is still possible (with reduced chance of success) up to 10 days after the silk emerges.For this reason,developing ears of corn can be taken from the field,lightly dehusked with a sharp knife, and shaken to assess the progress of pollination by how much corn silk has fallen off.

Functions 

The silks,which are part stigma and part style,provide a female flower surface to which pollen grains can adhere and define the path along which the pollen must travel.The stigma is the very tip of the silk,which has more hairs to help the pollen adhere to it.Kernel formation in the cob requires pollination of the outer corn silk by wind or insects.There are usually several grains of pollen attached, but only one will successfully participate in the fertilization of the ovule to form the corn kernel.For the pollen grain,the male gametophyte,to transfer its genetic material to the ovule,it must germinate and form a pollen tube that extends nearly the full length of the corn silk strand.Typically 400 to 600 cores are successfully formed this way.The pollen tube extends at a rate of more than 1 centimeter per hour,and it takes only 24 hours to form a foot-long channel in the intercellular space of the ear of corn through which sperm cells (gametes) fertilize the ovule with the female gametophyte.The pollen tube is produced by a single vegetative cell in the pollen grain,which enters the tube with its cytoplasm,nucleus,and two sperm cells.The tube extends itself only at the apex,and the direction of apical progression responds to cyclic AMP levels,including cAMP cyclization by pollen signaling protein (PSiP),in an actin polymerization-dependent process.The ear of corn can control the type of pollen the ear receives by expressing some form of the gametophyte factor 1 gene.Many popcorn varieties of the everta type will greatly slow down the development of any pollen tubes that do not carry pollen of a similar form of Ga1-S or Ga1-M,thus preventing the genetic (natural or engineered) invasion of corn species from other species.Popcorn is still free to donate its genes to other types of corn through its own pollen.The effectiveness of this confinement can be measured by planting popcorn next to purple dent corn;if the kernels allow themselves to be fertilized by pollen from outside the group,the xenia effect leads to the formation of a purple aleurone layer.Organic farmers are looking to transfer some of these mechanisms to non-popcorn lines to prevent inadvertent pollination of GM corn, which could lead to their product being rejected as organic corn under U.S.regulations and their inability to resort to GM corn grower.

Pathology

Moisture in freshly grown silk sometimes attracts insects,which can cause silk shearing, which interferes with kernel formation.

Application

Corn silk contains a variety of pharmacologically active compounds and is therefore used in various folk medicines,including as a diuretic and as an inhibitor of melanin production.Many studies have proven that corn silk has antioxidant and health benefits.In addition,it is used as a diuretic,antidepressant,and antifatigue agent to reduce hyperglycemia.Corn silk is also used in teas and supplements for urinary problems.The antioxidant and hematopoietic protective effects of corn silk protein hydrolyzate have been proved by experiments.Potential antioxidant peptides in hydrolysates were also identified.