The larger of two nuclei in a pollen grain that controls pollen tube growth and elongation but does not participate in fertilization. It directs the cellular machinery needed for the pollen tube to reach the ovule.
From Latin 'tubus' meaning 'pipe' or 'tube' and 'nucleus' meaning 'kernel', referring to its role in controlling tube formation and growth. The term emerged in late 19th-century botanical literature as the dual nuclear structure of pollen grains became understood.
The tube nucleus is the unsung hero of plant reproduction - it works tirelessly to build the pollen tube highway but never gets to travel on it! After completing its mission of delivering sperm cells to the ovule, it simply degenerates, making it one of biology's most selfless cellular workers.
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