Energetics of Early Seedling Growth in Corn (Zea mays L.)1

Abstract

Early growth of the corn seedling was studied in relation to its dependence on energy from endosperm and early photosynthetic tissue. Measurements were made of (1) endosperm utilization rate of seedlings grown in light and dark; (2) growth and leaf area of seedlings as affected by partial endosperm removal; and (3) photosynthesis (P), respiration (R), and 14CO2 uptake of seedlings as affected by endosperm excision at different ages. Endosperm utilization and growth rates were similar in light and dark until the two‐leaf stage l0 days after germination. Regression of root and shoot growth on age was 15.4 mg/day and of root and shoot growth on endosperm weight loss was .65 mg/mg. Partial removal of the endosperm at seeding resulted in decreased growth of roots and shoots and indecreased leaf area per seedling. Apparent P was negative at 9 days of age and was greatest for seedlings with endosperm excised. Apparent P was positive and similar at days 11, 12, and 13 for seedlings with endosperm excised and was positive, and increased from day 11 to day 13 for seedlings with endosperm. Energy obtained from CO2 fixation was not equivalent to that supplied by the endosperm until the 10th day. At this time seedlings had two fully emerged leaves. Absorption of 14CO2 was similar for seedlings with and without endosperm, and increased with age as a result of increased leaf area and increased absorption per unit of leaf area. Endosperm removal resulted in greater translocation of 14CO2 to seedling roots.