Spad 502

At the full boll-setting stage under sunny and cloudless weather from 9:00 to 10:00 AM, the photosynthetic parameters of fully expanded leaves (fourth main-stem leaf from the apex) were determined using three randomly selected plants in the central two rows of each plot. SPAD-502 readings were used as a proxy of the chlorophyll content of leaves (SPAD-502, Minolta, Japan). A Li-6400 portable photosynthetic apparatus (LI-COR, Lincoln, NE, United States) was also used to measure the net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular carbon dioxide concentration (C_i), and transpiration rate (T_r). The fluorescence parameters of chlorophyll, including the primary light energy conversion efficiency (F_v/F_m), non-photochemical quenching coefficient (q_N), photochemical quenching coefficient (q_P), and effective quantum yield of PSII photochemistry (ΦPSII), were measured by an FMS2 portable fluorescence system (Hansatech instruments, King’s Lynn, Norfolk, United Kingdom). The F_v/F_m determination required leaves to be dark-adapted for half an hour (Song et al., 2019 (link)).

Cotton growth and development measurements were performed on plants in the central part of the experimental plot to avoid border effects. Leaf chlorophyll contents (SPAD values) were measured at 90 days after sowing (DAS) on the 4th fully developed leaf using a SPAD-502 (Konica-Minolta, Japan). Plant height, codes per plant, bolls per plant and height to node ratio were counted and calculated. Leaf area was measured following the procedure described by Monteiro et al.^{34 (link)} using a leaf area meter CI-202 (CID Bio-Science, Inc., USA) in the laboratory. Leaf area index (LAI) was calculated using the formula: LAI = (leaf area per plant x number of plants) / plant area (2 m²). Seed cotton was harvested twice (during October-2018 and November-2018.
For wheat, the chlorophyll content (SPAD value) and LAI were measured at 90 DAS. Chlorophyll content was recorded with three repeated readings per flag leaf using a SPAD-502 device (Konica-Minolta, Japan). Leaf area was measured following the procedure of Yin et al.³⁵ and using a leaf area meter (CI-202, CID Bio-Science, Inc., USA). The data of yield and yield contributing parameters plant height, spike length, grains per spike, spikelets per spike, plant biomass, and grain yield were recorded was recorded at maturity and following standard procedures.

The agronomic traits were determined for the investigation according to Liu et al. [66 (link)], and the main agronomic indicators include: maximum outer leaf soluble solids (MOSS), middle leaf soluble solids (MLSS), number of outer leaves (NOL), plant height (PH), maximum outer leaf width (MOLW), maximum outer leaf length (MOLL), maximum outer leaf area (MOLA), maximum outer leaf SPAD value (MSV), leaf head gross weight (LHGW), leaf head net weight (LHNW), root weight (RW), midrib length (ML), midrib width (MW), midrib thickness (MT), condensed stem length (CSL), leaf head height (LHH), leaf head width (LHW), and head length/head width ratio (HR). At the same time, referring to the method of Badu-Apraku et al. [67 (link)], ward minimum variance cluster analysis was performed on agronomic trait indicators. The soluble solid content was determined using a PAL-1 digital sugar meter (ATAGO Corporation, Tokyo, Japan). The chlorophyll content of Chinese cabbage was determined using a portable hand-held chlorophyll meter SPAD-502 (Konica-Minolta, Japan, SPAD-502). The Chinese cabbage leaf area was measured using a portable leaf area meter (Yaxin-1242, Beijing, China). All assays were conducted with at least three biological replicates.