DOI: 10.5061/dryad.pg4f4qrw5
title: Original data for for intercropped maize experiments, root barrier experiments in intercropped maize, and unilateral shading experiments

description: Intercropping improves resource utilization and yield; however, shading
 causes a decline in yield. Under wide-narrow-row maize-soybean
 intercropping, maize plants are subjected to weak unilateral illumination
 and exhibit high photosynthetic performance. However, the mechanism
 regulating photosynthesis under unilateral weak light remains unknown.
 Therefore, we conducted an experiment with different planting
 configurations and two controlled environments to investigate
 photosynthesis, sugar metabolism, and photosynthate allocation in unshaded
 and shaded leaves under weak light. All three experiments detected an
 increase in the net photosynthetic rate (Pn) of unshaded leaves on one
 side with an increase in the level of shade on the other side leaves. On
 the contrary, the concentration of sucrose and starch and the number of
 starch granules in the unshaded leaves decreased with increased shading
 due to the transfer of abundant 13C into the grains. However, sink loss
 with ear removal reduced the Pn of unshaded leaves, limiting their ability
 to transport sugar. Detailed analysis showed that intense unilateral shade
 (40% to 20% normal light) reduced grain yield (37.6% to 54.4%) but not
 mild unilateral shade (60% normal light). We further found that in
 unshaded leaves, Agpsl, Bmy, and Mexl-like significantly influenced
 sucrose and starch metabolism, while Sweet13a and Sut1 were crucial for
 sugar export. Sps1, Agpsl, and Sweet13c were crucial for sugar metabolism
 and export in shaded leaves. Thus, our study confirmed that under
 unilateral illumination, unshaded leaves, which transported photosynthates
 to the ear, contributed significantly to the grain filling and reduced
 sugar concentration, resulting in a higher photosynthetic performance,
 while the shaded leaves synthesized fewer photosynthates, primarily for
 their growth and development. We, therefore, propose a narrow-row spacing
 (40 cm) that provides appropriate unilateral shade (60% normal light) and
 limits yield reduction in a wide-narrow-row intercropping system.
description: # Original data for for intercropped maize experiments, root barrier
 experiments in intercropped maize, and unilateral shading experiments
 doi:10.5061/dryad.pg4f4qrw5 These datasets were collected between 2020 and
 2021 and include data from experiments involving different row spacings in
 intercropped maize, root barrier experiments in intercropped maize, and
 unilateral shading experiments. ### Description of the data and file
 structure The dataset includes: A) The photosynthetically active radiation
 (PAR) in the maize canopy during intercropping is measured in units of
 micromoles per square meter per second (µmol/m²/s). Please refer to the
 file "1. Photosynthetically active radiation" for specific data.
 B) To view the gas exchange parameters for the intercropped maize
 experiments with different row spacings, root barrier experiments in
 intercropped maize, and unilateral shading experiments, please refer to
 the file "2. 2020-2021 Gas exchange parameters." C) Unilateral
 shading experiment: Starch granule number and size. For detailed data,
 please refer to the file "3. Starch granule number and size." D)
 Unilateral shading experiment: Sucrose and starch concentrations at
 different time intervals. Please refer to the file "4. 2020-2021
 Sucrose and starch concentrations" for detailed data. E) Leaf dry
 matter weight (in grams), leaf 13C content, and grain 13C content for the
 unilateral shading experiment. For detailed data, please consult "5.
 Leaf dry matter weight and 13C content." F) Expression data for genes
 related to sugar and starch metabolism at different time intervals in the
 unilateral shading experiment. Please refer to the file "6.
 Expression of genes related to sugar and starch metabolism" for
 detailed information. G) Grain weight (in grams) and gas exchange
 parameters after ear removal for the unilateral shading experiment. Please
 consult the file "7. Grain weight and gas exchange parameters after
 ear removal" for detailed data. H) Yield data (in kilograms) for the
 intercropped maize experiments with different row spacings and root
 barrier experiments in intercropped maize for two years. Please refer to
 the file "8. 2020-2021 Intercropped maize yield" for detailed
 information. Abbreviations PAR: photosynthetically active radiation
 (µmol/m²/s) Photo: net photosynthetic rates (µmolCO2/m²/s) Ci:
 intercellular CO<sub>2</sub> concentration (µmolCO2/mmol)
 Cond:  stomatal conductance (µmolH2O/m²/s) BC: blank control, natural
 abundance isotope in organs I<sub>20</sub>,
 I<sub>40</sub>, and I<sub>60</sub> indicate
 intercropping maize, narrow (N) and wide (W) rows spacing of 20 + 200, 40
 + 180, and 60 + 160 cm, respectively. M represents monoculture maize with
 a row spacing of 70 cm, and CK represents monoculture maize with row
 spacing of 160 cm and plant spacing of 160 cm. L indicates the left side
 of the plant and R indicates the right side of the plant.
 SI<sub>20</sub>, SI<sub>40,</sub> and
 SI<sub>60</sub> indicate intercropping maize with split-root,
 narrow (N) and wide (W) rows spacing of 20 + 200, 40 + 180, and 60 + 160
 cm, respectively. SM: split-root, monoculture maize with a row spacing of
 70 cm. SCK: split-root, monoculture maize with row spacing of 160 cm and
 plant spacing of 160 cm. L represents the left side of the plant, and R
 represents right side of the plant. The leaves on the right side of the
 plants were exposed to normal light (non-shaded; NS) in all treatments,
 while the leaves on the left side of plants were shaded (S) and exposed to
 20%, 40%, and 60% normal light (T<sub>20</sub>,
 T<sub>40</sub>, and T<sub>60</sub>, respectively).
 Leaves of the whole plants exposed to 50% normal light and normal light
 were used as control 1 (T<sub>CK1</sub>) and control 2
 (T<sub>CK2</sub>), respectively. Capital letters (L and R)
 indicate the left and right side leaves of the plants, respectively.