Leaf chlorophyll, net gas exchange and chloroplast ultrastructure in citrus leaves of different nitrogen status.
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 (A(CO2)) and leaf water-use efficiency (WUE) reached maximum values in leaves with approximately 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 A(CO2) capacity at leaf N concentrations above 187 mmol N m-2 appeared to be correlated with the presence of numerous large starch granules.
University of Florida, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850, USA. bbondada@ucdavis.edu
Bhaskar R
BR
Bondada
James P
JP
Syvertsen
D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis / Q000502:physiology*; D002736:Chloroplasts / Q000502:physiology* / Q000648:ultrastructure; D002957:Citrus / Q000502:physiology*; D009584:Nitrogen / Q000172:deficiency / Q000502:physiology; D018515:Plant Leaves / Q000737:chemistry / Q000502:physiology*
D002734:Chlorophyll; D002245:Carbon Dioxide; D009584:Nitrogen