In vitro propagation of the rose rootstock 'Moneyway' was investigated on the following media: Murashige and Skoog (MS), Quoirin and Lepoivre (QL) and Woody Plant (WP). Growth, which was measured as length of shoots after a 6-week period, was faster on MS and QL than on WP. In spite of the better growth, chlorosis of newly formed leaves occurred from the third week on and was correlated with a lower chlorophyll content of shoots.

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The fate of nitrate and nitrogen‐15 was followed during the apparent induction phase (6h) for nitrate uptake by N‐depleted dwarf bean (Phaseolus vulgaris L. ev. Witte Krombek). Experiments were done with intact plants and with detached root systems. Qualitatively and quantitatively, xylem exudation from detached roots was a bad estimate of the export of NO−3 or NO−3‐15N from roots of intact plants. In vivo nitrate reductase activity (NRA) agreed well with in situ reduction, calculated as the difference between uptake and accumulation in whole plants, provided NRA was assayed with merely endogenous nitrate as substrate (‘actual’ NRA). The majority (75%) of the entering nitrate remained unmetabolized. Both nitrate reduction and nitrate accumulation occurred predominantly in the root system. Some (< 25%) of the root‐reduced nitrate‐N was translocated to the shoot. Nitrate uptake occurred against the concentration gradient between medium and root cells, and probably against the gradient of the electro‐chemical potential of nitrate. Part of the energy expended for NO−3 absorption came from the tops, since decapitation and ringing at the stem base restricted nitrate uptake.

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The rate of nitrate uptake by N‐depleted French dwarf bean (Phaseolus vulgaris L. cv. Witte Krombek) increased steadily during the first 6 h after addition of NO3 ‐After this initial phase the rale remained constant for many hours. Detached root systems showed the same time‐course of uptake as roots of intact plants. In vivo nitrate reductase activity (NRA) was assayed with or without exogenous NO3‐ in the incubation medium and the result ing activities were denoted potential and actual level, respectively. In roots the difference between actual and potential NRA disappeared within 15 min after addition of nitrate, and NRA increased for about 15 h. Both potential and actual NRA were initially very low. In leaves, however, potential NRA was initially very high and was not affected by ambient nitrate (0.1–5 mol m‐3) for about 10 h. Actual and potential leaf NRA became equal after the same period of time. In the course of nitrate nutrition, the two nitrate reductase activities in leaves were differentially inhibited by cycloheximide (3.6 mmol m‐3) and tungstate (1 mol m‐3). We suggest that initial potential NRA reflects the activity of pre‐existing enzyme, whereas actual NRA depends on enzyme assembly during NO3‐ supply. Apparent induction of nitrate uptake and most (85%) of the actual in vivo NRA occurred in the root system during the first 6 h of nitrate utilization by dwarf bean.