BIOSCI 108: Lecture 12 - Introduction to the ‘Green Kingdom' & New Zealand Flora

Plants

All plants are under the kingdom ‘plantae’.

They’re all photosynthetic, having the capacity to use sunlight, water, and CO2 to make energy-containing molecules and oxygen as a byproduct. They’re stationary, being stuck where they are. They have rigid cell walls made up of cellulose.

Some of them are embryophytes, meaning they form embryos as a way of reproduction. Some may also reproduce asexually

But many of them are very diverse due to the vast diversity of terrestrial and aquatic habitats. That means that they’ve had to evolved different morphologies, adopt unique adaptations, and having diverse communication methods to better suit their environments.

Importance of Plants

They provide food and habitat for essentially every other living being. Alongside that, they are also in-charge of many ecosystem services such as providing oxygen and being the drivers of biogeochemical cycles (evapotranspiration in water cycle, photosynthesis in carbon cycle, etc).

They’re also a major resource for humans whether that be for food, building, medicines, clothes, or so on. They have a lot of economic value whether that’s for farming/horticulture or tourism.

Plant diversity also supports animal diversity as well as having more plants opens up more niches and opportunities for a diverse range of animals to fill in.

Four Groups of Plantae

1. Byrophytes: These are your mosses, liverworths, hornworts, and so on. They’re considered the most simplest and ‘least evolved’ species of plants as they don’t have any vascular tissue to conduct water all throughout themselves.

2. Pteridophytes: These are your ferns. They do have vascular tissue, allowing them to grow out more complicated and longer structures. But they do not produce seeds.

3. Gymnosperms: Things such as conifers that make naked seeds and or cones.

4. Angiosperms: Flowering plants that do make closed seeds

Alteration of Generations

All plants have two generations of life that they cycle through. A gametophyte haploid (n) phase that produces gametes (n) through mitosis which is then fertilised to start a diploid phase. A sporophyte diploid (2n) phase that produces spores (n) through meiosis.

Plants cycle through these two generations.

Photosynthesis

The process of making carbon sugars by using solar energy, CO2, and water.

It is done in two major steps, the light reactions and the light-independent reactions.

The light reactions captures energy from incoming sunlight into temporary electron deliverers (ATP, NADPH) while water is needed to ensure that energy ‘holes’ from the transfer of electrons is filled up.

The light-independent reactions uses the energy captured into the electron deliverers to fix CO2 into carbon sugars.

Aotearoa’s Plants

Aotearoa has an extremely high level of endemic plants (~80%) meaning that we don’t see them anywhere else. This includes:

• Divaricating plants

• Large alpine flowers

• Heteroblastic species

• Small inconspicuous white flowers

Divaricating Plants

These are shrubs that have a very branchy and wirey pattern of growth. They look like a tangled network of thin stems that grow and spread out in different directions. It is thought that they adapted this to provide a natural protection against grazing, most likely from the moa. There also seems to be a latitudinal distirbution to it as well.

Large Alpine Flowers

Large floewrs seen in our alpine regions. It is thought that these plants have this adaptation to allow pollinators to spot them easily from further distances. Perhaps smell isn’t as reliable of an attractor in alpine regions. They also tend to be white flowers.

Heteroblastic Species

Species of plants that have different morphologies and shapes as they mature. These plants tend to have completely different leaf (or other parts) shapes between juvenile and mature states.

Small Incospicuous White Flowers

Similar to large alpine flowers, these small inconspicuous white flowers are thought to have these adaptations to better attract pollinators. Instead of investing their energy in making their flowers big, they instead focus more of other aspects, mainly scent. They’re also white as white is thought to be an attractor for generalist pollinator species.