STARCH CONCENTRATION AND IMPACT ON SPECIFIC LEAF WEIGHT AND ELEMENT CONCENTRATIONS IN POTATO LEAVES UNDER VARIED CARBON-DIOXIDE AND TEMPERATURE

Foliar concentrations of starch and major elements, nitrogen (N), phos phorus (P), potassium (K), calcium (Ca), and magnesium (Mg), along wit h specific leaf weight (SLW) were determined in the potato (Solanum tu berosum L.) cvs 'Denali', 'Norland', and 'Russet Burbank' grown for 35 days under CO2 concentrations of 500, 1,000, 1,500 and 2,000 mu mol . mol(-1) at both 16 degrees C and 20 degrees C air temperature. The st arch concentration, pooled from the three cultivars, increased with in creasing CO, concentration at both 16 degrees C and 20 degrees C and w as consistently higher at 16 degrees C than at 20 degrees C. The SLW ( g . m(-2)) was positively related to the foliar starch concentration o n the basis of leaf area or dry weight. The concentrations of N, P, Ca , and Mg in leaves were negatively related to starch concentration und er approximate to 14% starch on a dry weight basis. Above 14% starch, there was no significant relationship between element and starch conce ntrations. Similar patterns were seen when the SLW and element concent rations were expressed on a starch-free basis. In contrast, the leaf c oncentration of K was not closely related to the starch concentration because the K concentration was similar at varied CO2 levels. The resu lts of this study indicate that the changes in SLW and concentrations of N, P, Ca, and Mg in potato leaves only partially resulted from the changed starch concentration.