Plants Biology 112

Kingdom Plantae  Multicellular eukaryotes that have cell walls made of cellulose  Develop from multicellular embryos and carry out photosynthesis using chlorophyll a and b  All are autotrophs but a few live parasitically or as saprobes (obtain food from decaying material)

Plant Reproduction  There are two alternating phases  Sporophytes are spore producing plants  Produced using meiosis  Gametophytes produce gametes  Produced by mitosis  Occurs after the spores have been produced

What Plants Need to Survive  Sunlight  photosynthesis  Water and minerals  All of their cells require both  Gas exchange  Plants require oxygen for respiration as well as carbon dioxide for photosynthesis  Movement of water and nutrients  Taken up by their roots but make food in their leaves

Early Plants  The appearance of plants created a lot of change to terrestrial environments  As a result, other organisms were able to develop  They began in the water, most likely evolving from a multi-cellular like organism similar to algae  Plants colonized land before animals did  Many biologists believe plants coevolved with fungi

First Plants  Algae are a plant’s evolutionary ancestor  Share many similarities  Contain chlorophyll  Cell wall composition  DNA sequencing  Earliest plants were similar to today’s mosses  Dependent on water or at least a moist environment

Overview of the Plant Kingdom  Three features dictate the structural arrangement of plants  Water conducting tissues  Seeds  Flowers  There are four major groups: mosses, ferns, cone-bearing and flowering plants

Bryophytes (Mosses and relatives)  Also called non-vascular plants because they do not have vascular tissue (conducts water and other nutrients)  Depend on water for reproduction  Draw up water by osmosis which keeps them low to the ground  Produce sperm that must swim to reach the egg – therefore water is required

Mosses  Moist environments  Soil may lack nutrients  Can tolerate low temperatures  Contain a thin shoot with small leaves  They have rhizoids instead of roots

Liverworts  Flat leaves attached to the ground  Some are in the shape of a liver  Reproductive structures called gemmae – cup-like structures

Hornworts  Instead of gammae, hornworts produce a reproductive structure that looks like a horn

Life Cycle of Bryophytes  The gametophyte is the dominant, recognizable stage of the life cycle that carries out the plant’s photosynthesis  The sporophyte is the reproductive structure  A spore develops into a protonema and then develops rhizoids  Some plants produce both male and female on a single plant

Human Use of Mosses  Sphagnum moss is a group of mosses that grow in acidic environments  Acts as a natural sponge  Large deposits can turn into peat, which can be used as a fuel  Added to soil to increase its ability to absorb water  Also increases a soil’s acidity