Sentence:  However, sustainable avocado production at acceptable commercial levels remains a challenge as the <WSD>polyaxial</WSD>, pseudo-terminal flowering architecture of avocado (Verheij, 1986) dictates that trees must continuously increase in size to remain productive (Whiley and Schaffer, 1994). 
Meaning of the word marked with <WSD> tags:  Axial about more than one axis.