CITRUS ROOTSTOCK AND CARBON-DIOXIDE ENRICHED IRRIGATION INFLUENCE ON SEEDLING EMERGENCE, GROWTH, AND NUTRIENT CONTENT

Seeds of Carrizo citrange (Citrus senensis (L.) Osb. X Poncirus trifol liata (L.), Cleopatra mandarin (C. reticulata Bianco), Sour orange (C. aurantium L.), and Rough lemon (C. limon (Burm f.) were sown in trays , irrigated without or with enriched Carbon dioxide (CO2) (1,362 mg L( -1)) and evaluated for seedling emergence, growth, and nutrient conten ts. Rough lemon had a faster rate and higher percent emergence than th e other rootstocks. Carrizo citrange had thicker stem diameters and ta ller seedlings than other rootstocks. Cleopatra mandarin had the small est seedling shoot and root weights and larger shoot:root ratios than Rough lemon and Sour orange. Carrizo citrange and Cleopatra mandarin h ad higher leaf chlorophyll-a and total chlorophyll content than Rough lemon or Sour orange. Carbon dioxide enriched irrigation had no effect s on emergence or seedling growth variables except lower root weight. Lower media pH (6.90 versus 5.65), attributed to CO2 enriched irrigati on, may have adversely affected root growth as compared to shoot chara cteristics. Leaf nutrient contents generally differed between rootstoc ks but were not affected by CO2 enriched water except for higher Zn an d lower Mn contents. These results indicate that citrus seedling emerg ence, subsequent growth and leaf nutrient content differred between ro otstocks but there are no beneficial effect from CO2 enriched irrigati on.