Abbreviations: CrAx, crown axile root; DW, dry weight; PPFD, photosynthetic
photon flux density; PrLat, primary lateral roots; SeLat, seminal lateral
root; SPAD, chlorophyll content (Soil Plant Analysis Development); ΦPSII,
operating efficiency of photosystem II
∗ Corresponding author. Tel.: +41 44 6323829; fax: +41 44 6321143.
E-mail address: andreas.hund@ipw.agrl.ethz.ch (A. Hund).
m Deceased 17 March 2004