While anchored in Dusky Sound, Fiordland on the South Island in 1773, Captain Cook brewed a healthy beer for his crew using branches from the rimu tree. Here’s the recipe in case you’re interested in brewing up a batch.
Plants are classified into two big groups, those that make seeds and those that don’t. Plants that don’t produce seeds reproduce by the use of spores. An example is ponga, the silver tree fern, talked about in a previous post, which uses spores to reproduce.
The seed-producing variety of plants, which include most plants, are then split into two other main groups, 1) those that have naked seeds (gymnosperms) meaning the seed is not enclosed by a fruit after fertilization and 2) those that produce flowers and enclosed seeds (angiosperms). Pine trees are an example of a gymnosperm; they produce no flowers but instead have pine cones in which seeds form.
But wait, why am I saying all this. Is this just some biological hoopla or fancy words? No, it is because even though many of these plants are fascinating in and of themselves, it adds another dimension of appreciation if one knows a little about their biology. So stay with me!
Remember how the ponga fern (you did read that blog, didn’t you?) produced a tiny gametophyte plant completely separate from itself. That little separate gametophyte generation on the ground was dependent on water in the environment for the sperm to swim, find the egg and for fertilization to occur. That’s why ferns are generally in watery or misty locations. And once fertilized, the fern plant has to immediately start growing into a plant regardless of the conditions and immediately either survives or doesn’t. The difference with seed plants is that they produce this gametophyte (fertilization) generation entirely on and within themselves.
In seed plants, fertilization takes place on the main plant itself, for example, in a pine cone or a flower, not as a distant vulnerable entity on the ground. Once fertilization in a seed plant occurs, a seed is produced which consists of a protective coat, nutrients inside to feed the plant when it starts to grow and the fertilized egg or plant embryo itself.
Hence when a seed is dispersed, it isn’t forced to try and grow right away. First, it has the outer coat which protects it and buys it some time. Now it will only sprout when conditions are favorable, and also it has a little built in supply of food with it to help get it started. All this is a considerable advantage over plants such as ferns, which is why seed plants can be considered more advanced than plants such as ferns.
So essentially ferns evolved first, followed by gymnosperms and then followed by angiosperms.
If we further subdivide the gymnosperms, our naked seed group of plants, one of the families in that group are the podocarps, a word referring to the seeds on a ‘fleshy foot’ that this family of plants produce. The podocarps evolved in Gondwana, that giant landmass that made up Africa, South America, Australia and New Zealand, 135-190 million years ago during the Jurassic Period, reaching their peak about 50 million years ago. Many of them subsequently disappeared but when Gondwana split up, some were dispersed on the various land masses including what became New Zealand.
Rimu (Dacrydium cupressinum) is a podocarp tree endemic to New Zealand. The remaining stands of this chiefly tree are found mainly on the North Island. Most trees are 20-35 m in height with average lifespans of 500-600 years but some live up to 1000 years.
When you see the tallest rimu trees, it is often difficult to see their top branches. The trunks are so tall and straight with only a relatively small tuft of green at the top. Also so many other plants, vines and perching plants, make their lives in these giant trees, making it hard to distinguish which are the tree’s own leaves.
The Maori name for the plant, rimu, likens the foliage to a seaweed in Polynesia. Maori used the resinous heartwood for torches. The bitter gum was used to stop bleeding and leaves used on sores.
A second podocarp endemic to New Zealand is kahikatea (Dacrycarpus dacrydiodes), New Zealand’s tallest tree. Once one of the most common trees in lowland swampy forests, now only small stands of this magnificent tree remain mostly on the North Island. It grows to over 150 feet. The trunks are long and slender with a ragged crown of branches with scale-like leaves, 1-3 mm long.
It was first described by Daniel Solander, one of Captain Cook’s botanists who unfortunately died before returning to England. The small berries (koroi) were feasted on by the Maori.
Pollen is the powder produced by plants that contains the progenitor cells called microgametophtes that produces male gametes (sperm cells), the male half of the sex act for plants. Pollen is produced by plants by the millions and millions. It can be found covering our car on a spring day. It can make us sneeze and produce allergic reactions. In gymnosperms, pollen is generally released from separate male pine cones and is wind-blown and finds its way to female pine cones where fertilization occurs. In flowering plants, it is carried from one plant to another primarily by bees, moths, birds and other insects. The shape and size of pollen is unique for each plant and can be used to identify the plant from which it came. Here is a scanning electron microscopic view of various pollen.
Scientists have discovered kahikatea’s pollen and leaves in Jurassic rocks 160-180 million years old. This was before flowering plants (angiosperms) or birds had evolved. Indeed, it is speculated that kahikatea’s seeds were probably feasted on by pterodactyls (flying dinosaurs). Because of this, kahikateas are sometimes called dinosaur trees. This is one ancient plant. Pollen grains of rimu’s ancestors (discussed above) have also been found in fossils 70 million years old.
Where are the rimu and kahikatea trees now? Both trees still exist but primarily in protected forest areas. After the arrival of the Europeans, both rimu and kahikatea trees were extensively milled. Rimu was used extensively to build houses and make furniture. The number of Jurassic kahikatea were markedly diminished long before its ancient past was realized in order to make . . . butter boxes.
That’s right, in a sad chapter of history, most of the kahikatea trees were felled for butter boxes for the refrigerated export of 56 lb. slabs of butter in the 1880’s, as the wood was light-weight and did not taint the produce on its long sea journey. In 8 years alone, it is estimated the number of kahikatea trees were reduced by more than 60%.
People often tend to think of New Zealand as pristine and untarnished. But like most countries, it has not been immune from the often-cavalier destruction of life forms. Its history carries the scars of vast biological devastation: plants, birds, seals, whales, the moa.
Hasn’t this always been part of man’s history? At first, the necessity and expediency of survival itself often causes wanton devastation, and later as society becomes more advanced, economic interests complete the destruction.
The history of human life on earth is one of human-caused extinction of other species and the pace is accelerating. And countless other plants and animals are threatened or at risk for extinction.
So why are these ancient trees important and why should we care?
Extinction is forever. Once gone, you can’t bring things back. When a plant or animal becomes extinct we have irreversibly destroyed something of unknown value.
Ecosystems are more healthy and dynamic with more species. With loss of species, habitats and indeed all life on earth becomes more vulnerable. Biodiversity provides health.
On a more selfish level biological speicies provide us with food, fiber, medicines and aesthetic opportunities. More than half of all medical prescriptions in the US contain a natural plant or animal product.
Finally we are deprived of the learning opportunity to better understand the relationships among organisms and life itself.
Surely something 180 million years old such as the kahikatea has something to tell us . . . if we listen.