2.2.1. Crop Data

Specific leaf area (SLA) was calculated where one sided area of a fresh leaf was divided by its dry weight. For SLA, leaf area was calculated by the manual destructive method. SLA was measured at four growth stages, i.e., tillering, booting, heading, and maturity. Crop growth rate (CGR) was also calculated by recording the dry biomass at the abovementioned four growth stages selected for SLA. Hunt, in 1978, gave the following formula for the calculation of CGR:

$$\text{CGR} = \frac{\text{W}\_2 - \text{W}\_1}{\text{t}\_2 - \text{t}\_1}$$

where W2 and W1 are the dry biomass weights at the two respective growth stages and the difference of t2 and t1 is the time difference between the two respective growth stages.

Plant height was recorded at different growth stages by randomly selecting the 20 plant samples at each growth stage and the maturity average was taken. The number of productive tillers was counted by randomly selecting the 1-m2 area in each plot. For calculation of spike weight, spike length, and number of grains per panicle, 20 panicles of primary tillers were taken randomly from each plot and then the average was taken for each of these three parameters. To estimate the 1000-grain weight, 1000 grains were randomly weighed by taking five samples from each plot, and then the average was taken. The final grain yield was calculated after threshing the crop which was done at 14% grain moisture level. The record for time taken by a specific growth stage, namely phenological data record, was also noted for sowing, transplanting, tillering, booting, heading, grainfilling, and maturity. To have a record for dry weight accumulation and grain-filling rate at grain-filling stage, each plot was labeled with 200 panicles and the date of the labeling day was 0 days (d). Samples were taken at 1, 4, 8, 12, 16, 20, 26, 32, 38, and 44 d after labeling. A total of 10 spikes were taken each time, and separation and counting of superior and inferior grains was done. Grains were counted and separated through basic ideas about superior and inferior grains, i.e., grains of the three primary branches directly at the top were the superior ones, whereas the grains of the three branches at the bottom of the panicle were the inferior ones. After separation, superior and inferior grains were separately dried to have dry weight accumulation and grain-filling rate record for each plot. The dry weight accumulation was measured in mg grain<sup>−</sup>1, whereas the grain-filling rate was calculated in mg grain−<sup>1</sup> day<sup>−</sup>1. Using Richard's growth equation with reference to the formula given by [58], the grain-filling rate was calculated:

$$\mathbf{G} = \mathbf{kW} / \mathbf{N} (1 - (\frac{\mathbf{W}}{\mathbf{A}})^{\mathbf{N}})$$

where W is the grain weight (mg), A is the final grain weight (mg), t is the time in days (d) after anthesis, and B, k, and N are the constants/coefficients calculated after regression (data not given in results).

For calculation of time of day of anthesis (TOA) and duration of anthesis, a square of 1 m<sup>2</sup> area was selected. Every square was named as the sub-plot and was observed every day during the entire flowering period every 30 min or less, from sunrise until the termination of anthesis on the last spikelets about midday or early afternoon. Onset of anthesis is defined as the time of day when at least 5 panicles in the observational sub-plot started anthesis of at least one opened spikelet visible per panicle. The maximum of anthesis is when all panicles of the sub-population of panicles attained anthesis of at least one spikelet opened on every panicle, and the end of anthesis is when all the panicles in sub-plot terminated the anthesis as shown by stamens' droopiness, change of color of stamens, and spikelet closure. The TOA was expressed as hours after sunrise (hasr) and duration of anthesis was noted in hours (h).
