Fertilization Response on Growth, Photosynthesis, Starch Accumulation, and Leaf Nitrogen Status of Cassia siamea Lam. Seedlings Under Nursery Conditions

Nitrogen, phosphorus, and potash fertilizers in eight treatment combinations, including an unfertilized control treatment were given to Cassia siamea seedlings under nursery conditions. This study was carried out to identify the physiological basis of varying growth response due to fertilization. Nitrogenous fertilizer application increased seedling growth, whereas application of phosphorus or potash fertilizers, either separately or in conjunction, did not improve seedling growth. Starch level had increased considerably whenever there was decline in the leaf nitrogen status, even though the photosynthetic rate was reduced drastically. Starch concentration remained significantly higher in leaves of seedlings which showed poor growth because of treatment effects. Vector analysis of nitrogen concentration, content, and dry mass allowed simultaneous comparison of leaf nitrogen status. This analysis showed that nitrogenous fertilizer application signified dilution effect. P-fertilizer application alone leads to N-deficiency and in PK-fertilizer application, vectors shifted into a region of antagonistic effect. These results are useful in evaluating woody seedlings growth response due to fertilizer management under nursery conditions.