The numerical taxonomy of plants is based on which of the following ?

All observable characteristics

The correct answer is Option (1) – All observable characteristics

Numerical taxonomy, also known as numerical phenetics or phenetic taxonomy, is a method of classifying organisms based on quantifiable similarities and differences in their observable characteristics. It relies on statistical analyses of data related to various traits or features of organisms, without necessarily considering their evolutionary relationships or underlying genetic mechanisms.

Therefore, the numerical taxonomy of plants is primarily based on all observable characteristics that can be quantitatively measured and compared among different plant species. These characteristics may include morphological features such as leaf shape, flower structure, fruit type, and stem architecture, as well as physiological traits, ecological adaptations, and geographic distribution patterns.

By collecting and analyzing numerical data on these observable characteristics from a wide range of plant species, numerical taxonomists aim to identify patterns of similarity and difference that can be used to classify plants into distinct groups or taxa. These groups are then organized into hierarchical classification systems, such as orders, families, and genera, based on the overall similarity of their quantitative traits.

In summary, numerical taxonomy in plants relies on the quantitative analysis of all observable characteristics to classify and organize plant species into taxonomic groups based on their similarities and differences.