Definition of micropyle in US English:

noun

• 1A small opening in the surface of an ovule, through which the pollen tube penetrates, often visible as a small pore in the ripe seed.

  Example sentences

  • ‘Only one pollen tube tip entered the nucellus through the micropyle.’
  • ‘It remains to be studied exactly how the pollen tubes reach the micropyle of the ovules.’
  • ‘The ovule micropyle and embryo sac were penetrated equally by cross- and self-pollen tubes.’
  • ‘However, pollen tubes from control pollen showed normal morphology when growing towards the micropyle of an ovule in a HTS plant.’
  • ‘Within the ovary, pollen tubes also grew in the ECM to penetrate the micropyle and subsequently grew intercellularly within the nucellus up to the embryo sac.’

  1. 1.1Zoology A small opening in the egg of a fish, insect, etc., through which spermatozoa can enter.
     Example sentences

     • ‘Coupling these screens with a visual assessment of seed formation has yielded mutants defective in FG development or in the ability of pollen tubes to release their sperm after entering the micropyle.’
     • ‘Sperm enter the anterior end of the egg through the micropyle.’
     • ‘In a favorable situation, an opening called the micropyle appears and releases amoebocytes, which differentiate into cells of all the other types.’
     • ‘Each cupule is recurved, has a lip-like projection near the point of attachment, and contains several ovules arranged in a curved row with their micropyles facing the cupule opening.’