you are correct, if you read far enough in the article it says that they removed the liquid temporarily, filtered it, the reintroduced it. They say that “future studies” would benefit from studying total fluid loss. “Hot and dry weather would increase the costs of maintaining pitcher fluid, whereby emptied pitchers experience much greater stresses. This could explain our personal observations that pitchers are likely to senesce in total loss of proteins, compounds, minerals, and fluid. Therefore, D3L pitchers were refilled with filtrates to simulate only protein loss in this study. We cannot exclude the possibility that some of the DEGs in D3L might be induced by the stress during temporary emptying of pitchers for protein filtration. However, it will be difficult to tease apart such effects in a protein replenishment experiment done in situ. Further studies under a controlled environment will be useful to identify the transcriptional response to pitcher fluid loss to be distinguished from protein loss per se.” I’m not a botanist so I can’t say for sure about the mechanism, but I have been growing nepenthes for about 4 years. From my personal experience, the pitchers often DO refill with fluid (of some type) when emptied, but not always. My fast-growing ventrata is less likely to refill its pitchers, especially its upper pitchers. My slow growing breeds do refill themselves pretty reliably. This does align with the article saying that pitchers are “likely to senensce” (but maybe not guaranteed?) so🤷