Biochemical indicators and iron index for the appraisal of the mineral status in leaves of cucumber and tomato

Abstract

The precision and usefulness of various foliar techniques in making valid diagnoses of mineral imbalances in plants have seldom been critically evaluated. This paper compares the classical critical value approach with the newer Biochemical Indicators Index (BI) in evaluating diagnoses from the same sets of data. The critical value and sufficiency range norms for various crops are presented and the Biochemical Indicator Index and Iron Index are calculated for comparative purposes. Although the norms for both approaches begin at similar reference points, the BI approach is able to make more meanigful diagnoses over a range of plant ages and can classify the order in which nutrients limit yield. Comparisions of diagnostic precision between the two systems are made using data from various greenhouse experiments with cucumber (Cucumis sativus L. cv. Pepinex) and tomato (Licopersicum esculentum Mill cv. Sarky). All plots received year the some rates of fertilizers consisting of 75 gm^‐2 iO gm^‐2, 20 gm^‐2 and 30 gm^‐2 of N; 30 mgm^‐2 of Fe, 10 mgm^‐2 of Mn; 5 mgm^‐2 of Zn and 2 mgm^‐2 of Cu.

Peroxidase, catalase, chlorophyll, carotenoid, anthocyanin, active and total Fe indexes established that low levels of fertility affected yields.

The range of critical values for Fe can not guarantee the diagnosis of deficiency status in specific cases. Because of this, we think that research must be directed toward the knowledge of the degree of metabolic activities by bioelements. In this work, we apply several biochemical indicators of the functional activity of Fe as well as the enzymatic activities of catalase, peroxidase and Fe index.

We suggest that the iron activity coefficient is a suitable index for the specific and discriminative knowledge of iron deficiency because of the strong interrelationship with the enzymatic activities.

Key words:

• Plant analysis
• Critical value
• Biochemical indicators
• Iron Index