Land Plants
Green algae is the closest relative to land places which suggests land plants got there start in wet areas close to fresh water. Photosynthetic organisms are apart of the eukaryotic supergroup Archaeplastids and the land plants can be further grouped as Viridiplantae. Land plants are monophyletic.
%%Desiccation%% (excess water loss) is a struggle for land plants.
Bryophytes (mosses, liverworts, hornworts) are %%nonvascular%% plants that rely on surface moisture and exhibit desiccation tolerance (ability to withstand severe dehydration). These plants are unable to photosynthesis in a dry environment. They are less than 5cm tall, have a permeable surface and do not have roots. Water moves through bryophytes via diffusion.
%%Vascular plants%% are able to get water from the soil and regulate water loss which allows them to have a more stable level of hydration. They transport water through tube-like cells up to 100m in the air and have an impermeable surface since they have roots. Vascular plants can photosynthesis when conditions are dry. More than 95% of all land plant species are vascular.
Vascular plants all originated from a common ancestor (monophyletic). Lycophytes, ferns & horsetails, gymnosperms and angiosperms are the main subgroups of vascular plants.
| Vascular Plant | Distinct Feature |
|---|---|
| Lycophytes | Spore-dispersing Sister group to all other vascular plants Mostly small |
| Ferns and Horsetails | Gametophyte and sporophyte generations are free living Disperse via spores Mostly small |
| Gymnosperms | Ovules are not enclosed in carpel Pines and other conifers Produce seeds |
| Angiosperms | Flowering plants Have fruits Double fertilization Produce seeds |
A vascular plants above ground organs (leaves, stem and reproductive organs) are called the shoot.
| Plant Cell Types | Description |
|---|---|
| Epidermis | Outermost cells that protect the plant Enhance uptake of H2O, CO2 and nutrients |
| Vascular | Long distance transport of water, sugar and signals Xylem transports water Phloem transports carbohydrates |
| Ground Tissue | Remaining cells Parenchyma are thin walled cells that perform photosynthesis and storage, can divide further if stimulated |