The regression of water potential values with various parameters of grapevine such as yield, vigour is positive, to mean that as the water stress level decreases to more low (high stress) these parameters decrease. But sometimes I get negative relation. Is there any justification for this?

Also, water potential and variables such as total soluble solids, total anthocyanin, tannin, total polyphenol content, etc which normally have negative relation sometimes give positive relation in the regression outcome. What is meant by this type of results? How can I justify these results?

Thank you for collaboration!!