Under nonlimiting conditions for nutrients, water, and light, the growth of citrus rootstocks was generally less in the presence of lantana (Lantana camara L.) than when they were grown alone. Approximately 75% of the rough leaves plants died within 3 months. Cleopatra mandarin was the least-affected rootstock with about 20% reduction of the root and shoot dry weights. The growth of Milam, sour orange, and Swingle citrumelo was intermediate in the presence of lantana. Overall, the presence of lantana did not affect nitrogen content of roots, whereas nitrogen levels in shoots varied for the six rootstocks.
Accumulation of dry mass, total N, protein N, and soluble amino acid N in the developing fruit and seeds of bell pepper (Capsicum annuum L.) was determined at selected intervals following anthesis. The importance of photosynthesis to the growth and nitrogen (N) assimilation in the developing fruit wall plus placenta (FWP) and seeds was evaluated by comparing the growth and accumulation of reduced N in nonphotosynthetic and photosynthetic fruits (covered vs. uncovered). The growth rate of the FWP and seeds was similar under both conditions. After 65 days of growth, the fruits kept in the dark weighed about 15% less than those receiving illumination; seed weight was the same for both treatments. Total N content of the FWP or seed continued to increase up to 55 days after anthesis. The FWP accumulated over 90% of fruit's total N, and there were no significant differences between covered and uncovered fruits. Protein N accounted for about 50% of the total N present in both covered and uncovered fruits.
Nitrate reductase (NR) activity (NO2− produced in the dark and under anaerobic conditions) of 30-day-old fruit of Capsicum annuum L. was 2.2% that in tissues of a single leaf adjacent to each fruit (33 vs. 1500 nmoles/hr-g fresh weight). The optimal NR activity in one source leaf could only account for about 17% of the fruit’s total nitrogen accumulation, while the fruit’s own NR activity was almost negligible. Covered and uncovered fruits did not differ significantly in NR activities.