The S RNase arrests the growth of one of its components.  
The quartet1 mutation can be used to study "tetrads" in this tissue, and T. fornieri has been used to study the attractant effects of LURE proteins upon it.  The S RNase arrests the growth of one of its components.  The action of callase is critical for its maturation, and at maturity it is surrounded by two cell walls, the intine and the exine.  Following hydration, a tube grows from this structure to direct the delivery of its generative cell through a micropyle; the POP2 and POP3 gene products are important for this process in Arabidopsis.  Microsporangia are sacs containing this substance, which has frills or wings in many gymnosperms.  For 10 points, name this powdery substance found on anthers, which contains the male gametes of plants and is the allergen that triggers hay fever.
The quartet1 mutation can be used to study "tetrads" in this tissue, and T. fornieri has been used to study the attractant effects of LURE proteins upon it.  
pollen