Leaf Morphology

Shape Shifters

Extract from our online course Botany and its role in the ecosystem
Some plants exhibit morphological traits related to the environmental conditions in which they live. 

The most important physical factor which has the most impact on leaf shape is light.  Leaves that trail along the ground surface or are shaded by other vegetation get less light and tend to be larger. 

Using an Ivy leaf as an example

Ivy (Hedera helix) exhibits morphological traits dependent on its growth stage. The mature leaves of Ivy exhibit the flowers and fruits whereas the broader, lobed leaves are the immature leaves. The immature leaves tend to trail on the ground in the shade whilst the mature leaves climb to the light. The difference in shape and diameter between immature and mature leaf is thought to be in response to the need to photosynthesise, with the larger size of the immature leaf providing a greater surface area to gain maximum energy from sunlight.  The morphological difference may also be connected to the way that the immature plant takes up and transports nutrients via xylem and phloem (i.e. the need to develop shoots and grow quickly in order to reach light). In regards to evaporation, the larger immature leaf will not transpire as much as the mature leaf so can be bigger without risk of losing water. 

 

Getting Closer: Using a hand lens

Eye Spy....

Sometimes the only way to identify a plant is by looking to see how rounded or angled (square) the stem is; whether it is smooth or furrowed and whether hairs are present or absent.  To narrow down identification even further you may also need to determine the shape and type of hairs that are present.   

 

To identify some plants a microscope is needed, but for the most part a 10x magnification hand lens is sufficient for identifying most species out in the field. However, for closer inspection, you may want to use a 20x or 30x magnification hand lens.

To use a hand lens correctly, hold it to your eye and bring the plant up to the hand lens.  Allow time to focus – you may need to draw the plant closer towards the hand lens or further back to get it into focus.

 

Spring: What to look out for #4

Primroses (Primula vulgaris)

When you next come across primroses take a closer look at the centre of the flower to see whether it is pin-eyed or thrum-eyed.


Primroses (Primula vulgaris) have two varieties Pin-eyed and Thrum-eyed.  In the Pin-eyed variety, the pistil is longer than the stamens.  

In the Thrum-eyed variety the stamens are longer than the pistils meaning that the pollen bearing anthers are visible but the stigma is hidden. The word thrum refers to a threadlike part of a flower, such as the stamens.

Spring: What to look out for #3

Cherry Plum (Prunus cerasifera)

In February and March you may start to see white flowers appearing before leaves on roadside shrubs or small trees.  These could be the flowers of the Cherry Plum or of Blackthorn - the two plants can be difficult to tell apart in early Spring.

To tell Cherry Plum apart from Blackthorn, look to see if fresh new growth is green and that it is without thorns.  You may also see new leaves beginning to appear with some of the flowers (unlike Blackthorn which flowers a little later on bare dark branches).  The flowers develop in late summer into yellow or red edible fruits, whilst sloes,  the fruits of the Blackthorn, develop into blue/black fruits.

Prunus cerasifera in February

 

Spring Flowers

Snowdrops have delighted us and now other spring flowers will take their place.  It's not just the colourful, showy plants that are making an appearance - look out for the humble and easily overlooked Townhall Clock (Adoxa moschatellina).
 

Townhall Clock (Adoxa moschatellina)

Spring: What to look out for #2

Hazel Catkins

Hazel (Corylus avellana) has yellowish drooping male catkins and tiny red bud-like female flowers.  The male catkins appear in January/February.

(January) Male catkins of Hazel (Corylus avellana)

(February/March) Female flower of Hazel (Corylus avellana) showing the red styles

Hazel (Corylus avellana) is monoecious (separate male and female flowers appear on the same plant) with male catkins (referred to as Lamb's tails) appearing in early spring.  The female flowers develop into nuts in the autumn.  Because it is often coppiced it may never reach its full height or spread.

Hazel Twigs cut back in February

Spring: What to look out for #1

Lesser Celandine (Ficaria verna)

Look out for the dark green and glossy heart-shaped (cordate) leaves of Lesser Celandine, a member of the Buttercup or Ranunculaceae family.  The species name Ficaria refers to the Latin name for fig and the genus name verna refers to the Latin for spring.  There are 8-12 glossy yellow petals which look freshly polished in the spring sunshine.

Lesser celandine (Ficaria verna)

There are four sub-species of Lesser Celandine but the two most common are Ficaria verna ssp verna and Ficaria verna ssp fertilis. Ficaria verna ssp verna can be identified by the bulbils within its leaf axils after flowering.  

Bulbils displayed in the leaf axil