Sentence:  Enhanced fluorochrome accessibility, increased nuclease sensitivity and chromatin dispersion reflects an increase in chromatin decondensation which is a sign of greater transcriptional activity of the plant genome in <WSD>arbuscle</WSD> containing cells .... The branching progression of the fungus into the host cell provokes de novo synthesis of the periarbuscular membrane. The periarbuscular membrane derived from the peripheral plasma membrane completely surrounds the <WSD>arbuscle</WSD>. 
Meaning of the word marked with <WSD> tags:  The site at which a symbiotic fungus attaches to the roots of a plant and exchanges nutrients, etc., with it.