Seasonal and diurnal patterns of non-structural carbohydrates in source and sink tissues in field maize

Abstract

Background: Carbohydrate partitioning and utilization is a key determinant of growth rate and of yield in plants and crops. There are few studies on crops in field conditions. In Arabidopsis, starch accumulation in leaves is a negative indicator of growth rate.

Results: Here, we wished to establish if starch accumulation in leaves could potentially be a marker for growth rate and yield in crops such as maize. We characterized daily patterns of non-structural carbohydrate (NSC) at different growth stages over two seasons for maize hybrids in the field. In 27 commercial hybrids, we found a significant negative relationship between residual starch in leaves and plant growth, but not with final yield and biomass. We then focused on three typical hybrids and established a method for calculation of C turnover in photosynthetic leaves that took into account photosynthesis, leaf area and NSC accumulation. The ratios of stored NSC decreased from approximately 15% to less than 4% with ongoing ontogeny changes from V7 to 28 days after pollination.

Conclusion: The proportion rather than absolute amount of carbon partitioned to starch in leaves at all stages of development related well with yield and biomass accumulation. It is proposed that screening plants at an early vegetative growth stage such as V7 for partitioning into storage may provide a prospective method for maize hybrid selection. Our study provides the basis for further validation as a screening tool for yield.

Keywords: Carbon allocation; Hybrids; Maize; Non-structural carbohydrates; Ontogeny; Photosynthesis; Starch.

Fig. 1

Relationship of residual starch at the 9^th leaf expanded stage with the corresponding growth amount (a), relative growth rate (b), final yield (c) and maturity biomass (d) for 27 commercial maize hybrids in the 2015 season. Abbreviations: DM, shoot dry matter

Fig. 2

Seasonal changes of total above-ground biomass (DM) (a) and leaf area index (LAI) (b) in the 2016 season. * and ** indicate significance at P ≤ 0.05 and P ≤ 0.01, respectively. No significant difference among the points for certain sample time without asterisk marked. Abbreviations: DAS, days after sowing

Fig. 3

Diurnal changes of net photosynthesis rates in the newly expanded leaves at the periods of 7^th leaf expanded (a) and 13^th leaf expanded (b) and the ear leaves at 28 days after pollination (c) for maize hybrids. * and ** indicate significant levels at P ≤ 0.05 and P ≤ 0.01, respectively

Fig. 4

Diurnal changes of starch (solid lines) and total soluble carbohydrates (TSC, short dash lines) in the newly expanded leaves at the periods of 7^th leaf expanded (a), 13^th leaf expanded (b) and the ear leaves at 28 days after pollination (c). Maize hybrids Xianyu335 (XY335), Denghai605 (DH605) and Zhengdan958 (ZD958) are indicated by hollow square, circle and triangle, respectively

Fig. 5

Diurnal changes of starch (solid lines) and total soluble carbohydrates (TSC, short dash lines) in the main sink tissues at the periods of 7^th leaf expanded (a), 13^th leaf expanded (b) and 28 days after pollination (c). Stem and grain were characterized as sink at vegetative and reproductive stages, respectively. Maize hybrids of Xianyu335 (XY335), Denghai605 (DH605) and Zhengdan958 (ZD958) are indicated by hollow square, circle and triangle, respectively

Fig. 6

Diurnal changes of starch (solid lines) and total soluble carbohydrates (TSC, short dash lines) in the transport tissues at the periods of 7^th leaf expanded (a), 13^th leaf expanded (b) and 28 days after pollination (c). Sheath and stem were characterized as transport tissues at vegetative and reproductive stages, respectively. Maize hybrids of Xianyu335 (XY335), Denghai605 (DH605) and Zhengdan958 (ZD958) were indicated by hollow square, circle and triangle, respectively

Fig. 7

Relationships between final yield (a) and biomass (b) and the ratios of starch to daily carbon accumulation in leaves at different growth stages. Hollow square, circle and triangle represent for the stages of 7^th leaf expanded (V7), 13^th leaf expanded (V13), and 28 days after pollination (DAP), respectively. Black, red and blue points represent for XY335, DH605 and ZD958, respectively