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Physiological, Morphological, and Agronomic Responses of Hybrid, High Yielding, and Traditional Rice (Oryza sativa L.) Varieties to Age of Seedling and Spacing
Thesis Abstract:
A field experiment was conducted from May to October 2007 at the Central Experiment Station of the University of the Philippines Los Baños, to examine the physiological, morphological, and agronomic responses of three rice varieties to different spacing and seedling age; evaluate the effect of plant spacing on the number of productive tillers and grain yield of three rice varieties; and determine optimum combination for plant spacing and seedling age of three rice varieties for high crop growth and productivity.
The study used three rice varieties (PSB Rc 72H, PSB Rc 18, and Dinorado), three seedling ages (8-, 15-, and 20-day-old seedlings), and two levels of spacing (20 x 20 cm and 40 x 40 cm) as treatments.
There were significant varietal differences in the number of tillers hill-1, number of days to maturity, number of productive tillers hill-1, panicle length, number of panicles hill-1, dry matter partitioning, leaf area index, and number of leaves on the main culm. PSB Rc 72H significantly attributed to dry matter partitioning, producing the highest panicle length and number of leaves on the main culm. PSB Rc 18 produced the highest number of tillers hill-1, productive tillers hill-1, panicles hill-1, leaf area index, and had the longest days to maturity. Dinorado had the lowest values in all parameters measured.
Using different seedling ages significantly affected plant height, days to maturity, root pulling resistance, dry matter partitioning, leaf area index, specific leaf weight, phyllochron (day leaf-1), and number of leaves on the main culm. Plant height and days to maturity were significantly increased using 20-day-old seedlings. Dry matter content, leaf area index, and specific leaf weight increased significantly at 15-day-old seedlings. The shorter phyllochron, higher root pulling resistance, and number of leaves on the main culm were observed for eight-day-old seedlings.
Differences in spacing significantly affected plant height, number of tillers hill-1, number of productive tillers hill-1, panicle length, number of panicles hill-1, number of filled grain per panicle, root pulling resitance, dry matter partitioning, crop growth rate (CGR), leaf area index, and phyllochron. Most of these characters increased significantly at wider spacing.
Crop growth rate was significantly higher for PSB Rc 72H using younger seedlings (eight days old) with wider spacing. For PSB Rc 18, highest CGR was recorded with 15-day-old seedlings with closer spacing, while for Dinorado, high CGR was recorded with younger seedlings with closer spacing. However, significant responses on grain yield were observed only at closer spacing.
There was no significant difference on root aerenchyma cell number, size, and total aerenchyma cell area due to variety, seedling age, spacing, and their interactions.