NUTRITIONAL RESPONSES OF CITRUS ROOTSTOCKS TO SALINITY: PERFORMANCE OF THE NEW HYBRIDS FORNER-ALCAIDE 5 AND FORNER-ALCAIDE 13

This study assesses the nutritional behavior of the new citrus rootstocks Forner-Alcaide no.5 (FA-5) and Forner-Alcaide no.13 (FA-13) under saline conditions compared to that of their parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Eighteen month-old plants grafted with Valencia orange scions were used in the experiment. The plants were grown in a greenhouse and irrigated over an eight-week period with nutrient solutions to which different amounts of sodium chloride (NaCl) had been added, namely 0, 20, 40 and 60 mM. Relative growth and the uptake of major mineral elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] were then determined. It was noted that the reduction in relative growth caused by salt treatment was greater in plants grafted on PT than those on FA-13, FA-5 and CM. Increasing the salt level in the growth medium reduced the absorption of the above mineral elements in all scion-rootstock combinations. However, this decrease was generally more marked in plants grafted on PT than in those on CM and FA-5. Plants on FA-13 showed an intermediate behavior. Positive correlations were found between growth and mineral element uptake by salt treated plants. Nutrient uptake was also plotted against chloride (Cl) and sodium (Na) concentrations in leaves and roots at increasing salt levels. This showed that N absorption was closely correlated (inversely) with Cl content in leaves, whereas K, Ca and Mg uptakes were correlated (inversely) with Na concentration in roots. This suggests that the accumulation of saline ions impacts growth and nutrient uptake by citrus plants.     

COMPETITIVE RELATIONSHIP OF CAULIFLOWER (BRASSICA OLERACEA L. VAR. BOTRYTIS) AND NETTLE-LEAVED GOOSEFOOT (CHENOPODIUM MURALE L.) AND THEIR DIFFERENTIAL RESPONSES TO POTASSIUM LEVEL

Growth and competitive abilities of cauliflower (Brassica oleracea L. var. botrytis cv. ‘White Cloud’) and nettle-leaved goosefoot (Chenopodium murale L.) were investigated under glasshouse conditions. The two species responded differently to a reduction in potassium (K) levels in the medium. Growth of C. murale was reduced while that of cauliflower increased with reduced K levels. At 0.125 mM K, average reduction in shoot dry weight of C. murale grown in pure and mixed stands was 35% and 58%, respectively. Average competition indices and relative competitive ability indices were higher for cauliflower than for C. murale. In a replacement series design, cauliflower showed higher shoot dry weight at high and low K levels in the medium than that of C. murale. Relative yield total (RYT) was > 1 indicating differences in species demand for K and would suggest possible control of the weed by managing the applied K level in the field.