© 2003 Heron Publishing—Victoria, Canada
Leaf chlorophyll, net gas exchange and chloroplast ultrastructure in citrus leaves of different nitrogen status
Bhaskar R. Bondada (1, 2, 3) and James P. Syvertsen (1)
1. University of Florida, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850, USA / 2. University of California, Department of Viticulture and Enology, One Shields Avenue, Davis, CA 95616, USA / 3. Author to whom correspondence should be addressed (bbondada@ucdavis.edu) / Received July 22, 2002; accepted October 26, 2002; published online May 1, 2003
Summary
One-year-old ‘Cleopatra mandarin’ (Citrus reticulata Blanco) seedlings were raised in a greenhouse and fertilized with nitrogen (N) at four application frequencies. Nitrogen-deficient
leaves (86 mmol N m–2) had less chlorophyll per unit area, but a greater chlorophyll a:b ratio than N-fertilized leaves (> 187 mmol N m–2). Leaf dry mass per area (DM area–1) and total chlorophyll concentration increased linearly with increasing leaf N, whereas chlorophyll a:b ratio declined. Net
assimilation of CO2 (ACO2) and leaf water-use efficiency (WUE) reached maximum values in leaves with ~187 mmol N m–2. Nitrogen-deficient leaves exhibited small chloroplasts with no starch granules; grana and stroma lamellae that coincided
with the accretion of numerous large plastoglobuli in the stroma disintegrated. High-N leaves had large chloroplasts with
well-developed grana, stroma lamellae and starch granules that enlarged with increasing N concentration. The lack of an increase
in ACO2 capacity at leaf N concentrations above 187 mmol N m–2 appeared to be correlated with the presence of numerous large starch granules.
Keywords:
chlorophyll a:b ratio, Citrus reticulata Blanco, grana, photosynthesis, plastoglobuli, starch, thylakoid.
