The affix ṇamul comes after the roots śuṣ 'to dry' and pūr 'to fill' when the word ūrdhva denoting an agent is in composition with them.,
Thus ऊर्ध्वशोषं शुष्यति वृक्षः = ऊर्ध्वे शुष्यति 'the tree is dried up while it is still standing'. Compare यद्वोर्ध्वशोषतृणवद्विशुष्कः 'or wither like the up-heaved grass drying up' (Bhatti. III. 14); ऊर्ध्वपूरं पूर्यते 'is filled full to the brim'. Rule 3.4.46 applies here also.,