amount of light energy absorbed by the green foliage, the efficiency of the foliage to use the energy captured Transgenic potatoes (Solanum tuberosum L.) overexpressing Arafor biomass production, and the partitioning of the crop bidopsis thaliana (L.) Heynh. phytochrome B (phyB) have been reported to exhibit a substantially modified plant architecture, increased biomass to the harvested plant part. Because potato has photosynthetic performance, reduced photoinhibition, delayed leaf one of the highest harvest indices of major crops and senescence, and increased tuber yield. A greenhouse and a growth there may be little potential for significant shifts in total chamber experiment were conducted at Braunschweig, Germany, to biomass accumulation, genotypes with superior net phoelucidate the crop physiological basis for the yield differences between Abbreviations: CER, carbon exchange rate; CER max , light-saturated

amount of light energy absorbed by the green foliage, the efficiency of the foliage to use the energy captured Transgenic potatoes (Solanum tuberosum L.) overexpressing Arafor biomass production, and the partitioning of the crop bidopsis thaliana (L.) Heynh. phytochrome B (phyB) have been reported to exhibit a substantially modified plant architecture, increased biomass to the harvested plant part. Because potato has photosynthetic performance, reduced photoinhibition, delayed leaf one of the highest harvest indices of major crops and senescence, and increased tuber yield. A greenhouse and a growth there may be little potential for significant shifts in total chamber experiment were conducted at Braunschweig, Germany, to biomass accumulation, genotypes with superior net phoelucidate the crop physiological basis for the yield differences between tosynthesis will likely be needed for further yield immoderately phyB-overexpressing transgenic (Dara-5) and wild-type provement. Flynn et al. (1998), in a study of a historical potato plants. In the greenhouse experiment, Dara-5 leaves showed series of European potato cultivars, in spite of large a 23% greater leaf carbon exchange rate (CER) at light saturation,

This study was conducted to elucidate the crop physiological basis for yield differences frequently observed in experiments comparing top-dressing of N fertilizers with injection of ammonium or ammonium/urea solutions into the soil. The effects of diammonium phosphate injected at the two-leaf stage, calcium nitrate (NO 3 -N) broadcasted and incorporated before sowing, and a control without N fertilization (-N) were assessed from measurements of growth, N-uptake and N-partitioning, light interception, gas exchange, leaf anatomy and the activity of key enzymes of N-metabolism. The experiment was performed with spring barley (Hordeum vulgare L.) grown in 80-l containers in a vegetation hall in Braunschweig, Germany. The plants in the NH 4 -N treatment produced a 20 % higher grain yield than those in the NO 3 -N treatment. The grain yield superiority of the NH 4 -N plants was attributable to a higher number of ears per plant (+13 %) and more grains per ear (+6 %). The NH 4 -N plants exhibited lower concentrations of inorganic cations than plants supplied with NO 3 -N. In the NH 4 -N treatment, the light penetrated more deeply into the crop canopy and the NH 4 -N plants exhibited a higher leaf carbon exchange rate at the different leaf layers than the NO 3 -N plants. It is concluded that as opposed to predominantly nitrate nutrition, provision of a persistent source of ammonium enables plants to take advantage of the positive yield effect of mixed N nutrition.

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