We connect the observed under-abundances of Li and Be in dwarfs, with recent results on nuclear cross sections at low energies: for collisions of protons with atomic or molecular targets, the measured cross sections seem too high with respect to extrapolations for bare nuclei. Phenomenologically, these anomalous nuclear interactions can be described in terms of an e ective screening potential U lab in the range of few hundred eV: in the presence of the electron cloud, nuclei become more transparent to each other as if the e ective collision energy is aumented by U lab . This implies that fusion cross sections are enlarged and at the same time elastic cross sections are lowered. If something similar occurs in stellar plasma, the nuclear burning temperatures are lowered, whereas di usion processes are enhanced. We nd that the observed Li and Be abundances in the Hyades and in the Sun can be reproduced for e ective screening potentials of the plasma in the range of 600-700 eV, close to that found by experiments in the laboratory. subject headings: stars: abundance-nuclear reactions-di usion.