Plant morphology

In these studies transcriptome conservation patterns were found to mark crucial ontogenetic transitions during the plant life cycle which may result in evolutionary constraints limiting diversification.

[4] There are four major areas of investigation in plant morphology, and each overlaps with another field of the biological sciences.

For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts.

The reproductive structures are more varied, and are usually specific to a particular group of plants, such as flowers and seeds, fern sori, and moss capsules.

For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts.

For example, the fronds of Bryopsis plumosa and stems of Asparagus setaceus both have the same feathery branching appearance, even though one is an alga and one is a flowering plant.

The growth form of many cacti and species of Euphorbia is very similar, even though they belong to widely distant families.

The similarity results from common solutions to the problem of surviving in a hot, dry environment.

When an animal embryo begins to develop, it will very early produce all of the body parts that it will ever have in its life.

When the animal is born (or hatches from its egg), it has all its body parts and from that point will only grow larger and more mature.

Once the embryo germinates from its seed or parent plant, it begins to produce additional organs (leaves, stems, and roots) through the process of organogenesis.

[7] Branching occurs when small clumps of cells left behind by the meristem, and which have not yet undergone cellular differentiation to form a specialised tissue, begin to grow as the tip of a new root or shoot.

This directional growth can occur via a plant's response to a particular stimulus, such as light (phototropism), gravity (gravitropism), water, (hydrotropism), and physical contact (thigmotropism).

[9] Endogenous hormone levels are influenced by plant age, cold hardiness, dormancy, and other metabolic conditions; photoperiod, drought, temperature, and other external environmental conditions; and exogenous sources of PGRs, e.g., externally applied and of rhizospheric origin.

There is variation among the parts of a mature plant resulting from the relative position where the organ is produced.

The smaller and more succulent the plant, the greater the susceptibility to damage or death from temperatures that are too high or too low.

[15] Sakai (1979a)[14] demonstrated ice segregation in shoot primordia of Alaskan white and black spruces when cooled slowly to 30 °C to -40 °C.

Extraorgan freezing in the primordia accounts for the ability of the hardiest of the boreal conifers to survive winters in regions when air temperatures often fall to -50 °C or lower.

In boreal species of Picea and Pinus, the frost resistance of 1-year-old seedlings is on a par with mature plants,[16] given similar states of dormancy.

[17] The transition from early to late growth forms is referred to as 'vegetative phase change', but there is some disagreement about terminology.

How intermediates between the categories are best described has been discussed by Bruce K. Kirchoff et al.[21] A recent study conducted by Stalk Institute extracted coordinates corresponding to each plant's base and leaves in 3D space.

"This means the way plants grow their architectures also optimises a very common network design tradeoff.

Based on the environment and the species, the plant is selecting different ways to make tradeoffs for those particular environmental conditions.

"[22] Honoring Agnes Arber, author of the partial-shoot theory of the leaf, Rutishauser and Isler called the continuum approach Fuzzy Arberian Morphology (FAM).

Rutishauser and Isler emphasised that this approach is not only supported by many morphological data but also by evidence from molecular genetics.

"[24] Eckardt and Baum (2010) concluded that "it is now generally accepted that compound leaves express both leaf and shoot properties.”[25] Process morphology describes and analyses the dynamic continuum of plant form.

[31] In a detailed case study on unusual morphologies, Rutishauser (2016) illustrated and discussed various topics of plant evo-devo such as the fuzziness (continuity) of morphological concepts, the lack of a one-to-one correspondence between structural categories and gene expression, the notion of morphospace, the adaptive value of bauplan features versus patio ludens, physiological adaptations, hopeful monsters and saltational evolution, the significance and limits of developmental robustness, etc.

[33] Our conception of the gynoecium and the search for a fossil ancestor of Angiosperms changes fundamentally from the perspective of evo-devo.

[36] It is a well illustrated volume of 1305 pages in a very large format that presents a wealth of morphological data.

[37] Including continuum and process morphology as well as molecular genetics would provide an enlarged scope.