BASIC BOTANY
IN COMMON WITH OTHER living organisms, plants have the abilities to grow, reproduce themselves, respond to stimuli and – to a limited extent compared to most animals – move. What sets them apart from animals in particular, and defines plants as a group, is their ability, in almost all species, to manufacture their own food from inorganic building blocks. Fundamental to this ability is the process called photosynthesis, in which plants use energy from sunlight to convert carbon dioxide from the air and water into glucose. Oxygen is a by-product of this reaction. A pigment called chlorophyll is the agent that extracts from sunlight the energy needed to fuel the reaction; its coloration is what makes plants green.
The plants covered in this book are the most advanced of their kind in evolutionary terms. All have the ability to reproduce sexually and flowers are the means by which this process is achieved. Flower structure is as varied as it is complex, and the fact that whole books, including this one, can be devoted to detailing its diversity is testament to this. Flower structure is dealt with in more detail on page 10.
Among terrestrial plants the process of photosynthesis is difficult to demonstrate outside the laboratory. However, certain submerged aquatic plants, such as this Water Starwort, produce bubbles of oxygen when they are exposed to bright sunlight, indicating that photosynthesis is indeed taking place.
THE ROLE OF PLANTS IN ECOLOGY
The importance of plants in the global ecosystem, and at the local level, cannot be overstated. Not only do plants generate (through photosynthesis) the atmospheric oxygen that all animals need to breathe but, as a source of food, they underpin food chains across the world. Without plants, life on earth as we know it would not have evolved and could not survive.
The survival of plants and animals is inextricably linked at the general level, but there are plenty of highly specific instances of dependence, the relationship often hinted at by their English names. Without their namesake-specific foodplants, neither the Figwort Weevil (left) nor the Mullein Moth (right), shown here as a caterpillar, could survive.
Achene – one-seeded dry fruit that does not split.
Acute – sharply pointed.
Alien – introduced by man from another part of the world.
Alternate – not opposite.
Annual – plant that completes its life cycle within 12 months.
Anther – pollen-bearing tip of the stamen.
Appressed (sometimes written as adpressed in other books) – pressed closely to the relevant part of the plant.
Auricle – pair of lobes at the base of a leaf.
Awn – stiff, bristle-like projection, seen mainly in grass flowers.
Axil – angle between the upper surface or stalk of a leaf and the stem on which it is carried.
Basal – appearing at the base of plant, at ground level.
Basic – soil that is rich in alkaline (mainly calcium) salts.
Beak – elongate projection at the tip of a fruit.
Berry – fleshy, soft-coated fruit containing several seeds.
Biennial – plant that takes two years to complete its life cycle.
Bog – wetland on acid soil.
Bract – modified, often scale-like, leaf found at the base of flower stalks in some species.
Bracteole – modified, often scale-like, leaf found at the base of individual flowers in some species.
Bulb – swollen underground structure containing the origins of the following year’s leaves and buds.
Bulbil – small, bulb-like structure, produced asexually by some plants and capable of growing into a new plant.
Calcareous – containing calcium, the source typically being chalk or limestone.
Calyx – outer part of a flower, comprising the sepals.
Capsule – dry fruit that splits to liberate its seeds.
Catkin – hanging spike of tiny flowers.
Chlorophyll – green pigment, present in plant leaves and other structures, and essential in the process of photosynthesis.
Cladode – green, leaf-like shoot.
Clasping – referring to leaf bases that have backward-pointing lobes that wrap around the stem.
Composite – member of the daisy family (Asteraceae).
Compound – leaf that is divided into a number of leaflets.
Cordate – heart-shaped at the base.
Corm – swollen underground stem.
Corolla – collective term for the petals.
Cultivar – plant variety created by cultivation.
Deciduous – plant whose leaves fall in autumn.
Decurrent – with the leaf base running down the stem.
Dentate – toothed.
Digitate – resembling the fingers of a splayed hand.
Dioecious – having male and female flowers on separate plants.
Disc floret – one of the inner florets of a composite flower.
Drupe – succulent fruit, the seed inside having a hard coat.
Emergent – a plant growing with its base and roots in water, the rest of the plant emerging above water level.
Entire – in the context
