Silk Development and Emergence in Corn

Corn produces separate male and female flowers on the same plant.The ear represents the female flower of the maize plant.Severe soil moisture deficits can delay silking and disrupt synchronization of pollen release and silking availability,resulting in poor kernel set.Corn plants produce separate male and female flowers (a flowering habit known to trivia lovers as monoecious.) Interestingly,both flowers are initially bisexual (aka "perfect" flowers),But during development the female component (pistil),the male component (stamen) of the male flower and the male component (stamen) of the female flower are aborted,resulting in parthenocarpus (male) and spike (female) development.The filaments that grow from the ear buds are the functional stigmas of maize female flowers.Each filament is connected to a separate ovule (potentially a kernel).A given silk must be pollinated for the ovules to fertilize and develop into kernels.Each ear typically forms as many as 1000 ovules,although typically only 400 to 600 actual kernels per ear survive to harvest.By definition, growth stage R1 of a single ear is defined as a silk thread visible from the tip of the husk.The entire field was defined as being in growth stage R1 when silk was visible on at least 50% of the plants.The entire field definition for growth stage R1 is synonymous with the term "midfilament".

Silk elongation and emergence 

Silks begin to elongate from the ovule 10 to 14 days before the R1 growth phase or approximately at the V12 leaf stage.The elongation of silk starts from the ovule at the base of the cob,and then extends to the tip of the ear in turn.Due to this apical flower order of silk elongation,silks at the base (rump) of the ear usually emerge first from the husk,while silks at the tip usually emerge last. Full silk emergence usually occurs within four to eight days after the first silk emerges from the shell leaf.When the silk breaks out of the shell,it will stretch 1.5 inches per day for the first day or two,but gradually slows down over the next few days.Filament elongation occurs through the expansion of existing cells,so the rate of elongation slows down as more and more cells reach their maximum size. The elongation of individual silk stops shortly after the pollen is captured, germinated,and penetrates the silk.If there is no pollination, silk elongation stops about 10 days after silk emergence due to senescence of the silk tissue.Abnormally long silks may be a diagnostic symptom of unsuccessful ear pollination (Nielsen, 2018).Within 10 days after silk emergence,silk can still accept pollen grains to germinate,but the degree is decreasing.Most successful ovule fertilization occurs in the first 4 to 5 days after silking.Over time,the breakdown of silk tissue during its natural aging process limits the continued growth of pollen tubes.Silking usually occurs in tandem with pollen shedding,so silking duration is usually not an issue.However,sometimes this synchronization is disrupted by stress.Delayed or failed silk emergence due to severe drought stress may result in poor kernel set or sterile cobs if no remaining pollen is captured by the silk.Some hybrids bred for drought tolerance have very aggressive silk behavior, meaning silk elongation is more tolerant of drought conditions.Unfortunately, sometimes under "good" growing conditions,these hybrids will silk 4-5 days before any pollen is available.In this case,the first filaments to emerge (usually from the tail end near the ear) fail to pollinate,resulting in poor fruiting at the tail end of the cob.