That's a fungal plug, and the powder are the fungal spores.

这是一个真菌栓，这些粉末就是真菌孢子。

Experimental blends of concrete include these bacterial or fungal spores alongside nutrients in their concrete mix, where they could lie dormant for hundreds of years.

混凝土的实验混合物包括这些细菌或真菌孢子以及混凝土混合物中的营养物质，它们可以在那里休眠数百年。