Effect of vpd, K nutrition and root-zone temperature on leaf area development, accumulation of Ca and K and yield in tomato

Abstract

SummaryCrop scale experiments were carried out in 1998/99 to investigate the individual and interactive effects of vapour pressure deficit (vpd), root-zone temperature (RZT) and potassium nutrient feed concentration on the accumulation of Ca and K in shoot tissues, vegetative growth, fruit yield and quality in tomato (Lycopersicon esculentum Mill). RZT and K nutrition had no detectable effect on growth but high K nutrition (10.mM) compared with the low (4.mM) increased the accumulation of K in the leaves and older fruits. In contrast, severe deficiencies of K were detected in young expanding lea¯ets (0.66±0.75%) near to the shoot apex under high (0.1.kPa vpd) compared with control humidity (1.50±2.03%; 0.5.kPa vpd). The accumulation of Ca was either unaffected or increased in leaf tissue at high humidity. Fruits developing on trusses in the top half of the shoot had markedly lower K concentrations under high humidity. In contrast the concentration of Ca was increased in fruit. The area of individual leaves was initially increased and then decreased by high humidity, but these responses did not appear to affect above ground dry-matter accumulation within the 56.d exposure period but a larger proportion of assimilates was partitioned to the fruits. Reduced accumulation of K detected under high humidity appeared to exhibit a close relationship with reduced leaf expansion, lower yield and a decreased proportion of class l fruits. The relationship between vpd and K, Ca accumulation, leaf growth, assimilate partitioning and yield responses are discussed.