Sam Kurumthottical, TVanisri, KKAU2020-11-102020-11-102004172341https://krishikosh.egranth.ac.in/handle/1/5810154806PGThe bio-availability of the toxic heavy metals like cadmium and lead together with its selective retention sites in tomato (Lycopersicon esculentum Mill.) was one of the major concerns in the crop. For this, pro-calculated quantities of cadmium and lead were applied to the soil mainly as water-soluble sources (cadmium chloride and lead nitrate respectively) to assess the finite objectives envisaged in the study. In order to meet the objectives, a pot culture experiment was conducted in the Vegetable Research Farm attached to the Department of Olericulture, College of Horticulture, Vellanikkara during the rabi season of 2003 with five treatments and four replications. Pre-treatment analyses of all basic inputs and soil were carried out to quantify the possible inclusion of heavy metals from them. After providing pre-calculated quantities of metals in pots, 42 day old and uniformly grown tomato plants of variety Sakthi were transplanted to pots. The plants were allowed to establish till majority of the plants (50 per cent) were at the turning stage. Biometric observations on the plants due to the impact of the metals were recorded. Fruits as and when they turned ripe were harvested with proper acknowledgment to their identity in treatments for yield and its subsequent dry weight. At harvest, the plants were carefully uprooted, cleaned properly and separated into root and shoot portions. After recording the weight of each portions, these parts were taken for analysis. Post-harvest soil samples were also collected and analysed to see the extent of availability of major nutrients and heavy metals, particularly cadmium and lead. All the inputs including soil maintained variable amounts of cadmium and lead, with maximum metal load contributed from phosphatic sources. It is seen that growth of tomato plants in pots, particularly under the influence of different levels of cadmium and lead, manifested differential growth and development. Internally also, the plants exhibited differential metal load and retention patterns apart from recording variation in the uptake of major nutrients. A brief resume of the major influence of different levels of cadmium and lead in soil and on the tomato plants is presented hereunder. Variation in cadmium levels in soil could influence significant variations In the available nutrient status in post-harvest soil samples. Accordingly, an increase in metal load permitted enhanced potassium availability in soil while the same status had an opposite effect particularly with respect to the available phosphorus and nitrogen. The nitrogen content of root and shoot of tomato plants was seen to be positively influenced with higher levels of cadmium application. However, a reverse trend in nitrogen content was observed with lower levels of application except for the shoot portions observed from Treatment 4. Among the various plant parts analysed, the fruits maintained the maximum nitrogen content and this content was roughly observed to be twice as that of its content in roots. Enhancement in cadmium level in soil resulted in a corresponding increase in the phosphorus content of roots, shoot and fruits. As observed for nitrogen, fruit portion maintained the maximum phosphorus content. A very similar trend was noted for the potassium content in tomato, consequent to the application of different levels of cadmium. Much before an apparent growth or' yield reduction was noted in tomato with cadmium application, the tomato plants readily exhibited certain characteristic symptoms, which could be associated with the metal toxicity on that plant. Preliminary indications appeared on leaves with such leaves picking up yellowing and inter-veinal chlorosis depending upon the metal load. At high concentrations of the metal, invariable splitting up of the stem at the collar region leading to complete death of such plants has been noted. As concentration of the cadmium load increased beyond 1.5 mg kg" soil, the tomato plants failed to fruit and at the highest concentration of the metal envisaged in the study (2.0 mg Cd kg" soil), the very establishment of the transplanted tomato crop was questioned. However, the successful survival and fruiting of the transplanted tomato plants was noted only at lower levels of cadmium addition (0.5 and 1.0 mg Cd kg" soil). Lower doses of addition of cadmium had exhibited negative influence on growth and development in tomato with the manifestation of significant reduction in number of branches, leaf length, leaf number, plant height, the production of trusses and subsequent reduction in yield. Reduction in growth and yield of tomato plants from different levels of application of cadmium, necessarily brought significant reduction in dry matter yield, whose influence is clearly reflected in the roots, shoot and fruits portions underlining a negative influence of cadmium on the dry matter production. At all levels of cadmium application, there was sufficient retention of the metal in plant whether it is root, shoot or fruits Roots of tomato are seen to preferentially harbour more of cadmium than its other plant parts particularly at higher levels of addition. However, at lower levels of addition, shoots preferred to maintain more cadmium than its root portions. Increasing levels of lead invariably decreased the root nitrogen content . significantly while shoots content of nitrogen increased generally with lower doses of metal addition. Variation in, lead levels permitted a significant increase in the phosphorus content in roots, shoot and fruits. No specific trend was noted in the retention of potassium by roots while shoot portions indicated significant influence of the same by offering differential content of potassium in them. Among all the plant parts, fruits maintained the maximum nitrogen, phosphorus and potassium content. Higher doses of lead rendered some fruits, if not all with certain malformations. This together with the total absence of any phyto-toxicity testifies that the tomato plants are able to tolerate high concentrations of lead inside them. Quite contrary to the expectations, an unusual increase in dry matter production was observed from lead treated tomato plants. Lead application in soil, irrespective of its levels, permitted maximum accumulation of the metal in fruits followed by shoots and roots. All accumulations noted in the plant were observed to be significant, projecting serious concern for the silent inclusion of lead in the economically important part of the plant. Variable amounts of cadmium and lead have been detected in the post-harvest soils indicating that the entire quantity of the applied cadmium and lead could not be completely absorbed by the plant.EnglishThesis