Update 2 files

- /assays/plant_phenotyping/protocols/phenotype_at_flowering.txt
- /assays/plant_phenotyping/protocols/phenotype_at_flowering.md

assays/plant_phenotyping/protocols/phenotype_at_flowering.md

+## Phenotype plants at flowering
+
+- when plants were scored as flowering (by awn emergence on the main culm, Zadoks stage 49, Zadoks et al. (1974))
+- all data was scored on the first emerging shoot (main culm)
+
+**Phenotypic data:**
+- plant height (distance from soil to the flag leaf ligule, in cm)
+- leaf number
+- tiller number (all tillers emerging after the main culm)
+- leaf length (leaf blade length from ligule to leaf tip, in cm)
+- leaf width (at the widest position of the leaf, in cm)
+
+**References:**
+
+Zadoks JC, Chang TT, Konzak CF. A decimal code for the growth stages of cereals. Weed Res. 1974:14(6):415–421. https://doi.org/10.1111/j.1365-3180.1974.tb01084.x
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