EFFECTS OF NITROGEN ON DEVELOPMENT AND GROWTH OF THE LEAVES OF VEGETABLES .1. APPEARANCE, EXPANSION GROWTH AND LIFE-SPAN OF LEAVES OF BRUSSELS-SPROUTS PLANTS

Leaf growth and development of Brussels sprouts (Brassica oleracea L. var gemmifera DC) was studied in three experiments, as affected by amo unt and timing of nitrogen application. Rate of leaf appearance, leaf expansion, leaf size and leaf senescence were extensively recorded. Th e rate of leaf appearance ranged between 0.39 and 0.72 d(-1). It was s ignificantly increased by more nitrogen. The rate of leaf expansion an d mature leaf area depended on leaf number and nitrogen treatment: the y increased with leaf number, reaching a maximum between leaf numbers 10 and 20 and decreased subsequently. Leaf expansion rate was the main factor determining mature leaf area, but the duration of expansion al so played a role: it was shorter for larger leaves. Plants receiving m ore nitrogen had a higher total green leaf area per plant, because of more and larger green leaves. Specific leaf area of all leaves decline d gradually from 130-230 cm(-2) g(-1) (depending on experiment) at abo ut 30 days after planting to 60 al the end of the experiments and was usually significantly increased by more nitrogen.