Present study was undertaken to elucidate the relationship between uptake of nutrients and photosynthetic activities, and the translocation of several mineral nutrients in rice plants which were grown under different cultural conditions, utilizing radioactive tracer technique.
Particular emphasis was placed on the analysis of patterns of nutrient uptake, the relationship between nutritional conditions and yield components. For this, rice plants grown on either low or high yielding fields at different growth stage were subjected to this study.
The results are summarized as follows;
1. Varietal difference was observed in the uptake of potassium and phosphorus. Kusabue and Jinheung had good capacity but Paldal had rather poor capacity for the uptake of the both nutrients.
2. For rice plants, a high positive correlation was found between the oxidation of alpha plaus-naphthylamine by root and uptake of phosphorus.
3. Carbon assimilation rate repended on rice varieties. It was high in Noindo, Gutaenajuok #3 Suweon #82 and Jinheung but low in Taegujo, Kwanok, Yugu #132 etc. 4. Heavy application of nitrogen increased carbon assimilation in rice plants but this also depressed translocation of certain carbohydrates to ears.
5. Carbon assimilation wan greatly hampered in rice plants deficient in magnesium, phosphorus or potassium.
6. Total dry matter after ear formation sage, was much higher in rice plants grown in high yielding fields than those grown in low yielding fields.
7. Leaf area index(LAI) reached maximum at heading stage and decreased thereafter in high yielding fields. But in low yielding fields, it reached maximum before heading and sharply decreased thereafter due to early senescence of lower leaves.
8. In general, light transmission ratio (LTR) of leaves was higher in the early growth stage and lower in later stages. Higher ratio of LTR to leaf area index, was found in the rice grown in high yielding fields than these in lew yielding fields.
9. Net photosynthetic activity decreased with the increase in leaf area index but was higher in high yielding fields than in low yielding fields.
10. After the ear formation stage, nitrogen, potassium and silicon as weil as K₂O/N in straw were higher in high yielding fields than those in low yielding fields.
11. Nitrogen, phosphorus, potassium and magnesium taken up by rice plants in low yielding fields before heading stage were readily translocated to ears than these in high yielding fields. This suggests greater redistribution of nutrients in straw occurs due to lower uptake, in later growth stages, by rice plants grown in low yielding fields and hence results in early senescence due to nutrient deprivation.
12. In the high yielding fields nitrogen uptake by rice was slow but continuous throughout the life of the plants resulting in a large uptake even after heading. But, in low yielding fields the uptake was fast before heading and slow after heading.
13. A high positive correlation was found between the contents of nitrogen and potassium in the straw at heading stage and grain yield. Positive correlation was also found to hold between the contents of potassium, silicon, K₂O/N, SiO₂/N in the straw at harvesting stage, and grain yield.
14. Carbon assimilation was greatly hampered in rice plants deficient in magensium, phosphorus or potassium.
15. Uptake of nitrogen, phosphorus, potassium, silicon and manganese by rice was considerably higher in high yielding fields and reached maximum at ear formation stage.
16. In rice, a high positive correlation was discovered between total uptake of nitrogen, phosphorus, potassium, calcium, magnesium, silicon, manganese at harvesting stage and grain yield.
17. In rice, a. high positive correlation was found between the total uptake of nitrogen, phosphorus, potassium, calcium, magnesium, silicon at harvesting stage, and number of spikelets per 3.3㎡. In addition, a correlation was found between the total uptake of nitrogen and potassium and number rf panicles per hill.
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