Chapter 37

 Plants need a variety of things to live:  Water and carbon dioxide  Chemical elements  Minerals  Soil  Nitrogen

 Soil, air and water all contribute chemicals to plants  Plants extract mineral nutrients from the soil in the form of inorganic ions.  Water acts as a solvent; provides the majority of a cell’s volume; and keeps cells turgid

 Organic materials include cellulose and sucrose  C, H, and O are the most abundant elements in plants  N, S, and P are the next most abundant

 17 essential elements have been identified in plants.  9 are macronutrients because they are required in large amounts (C, O, H, N, P S, K, Ca, Mg)  The remaining 8 are micronutrients (Cl, Fe, Mn, B, Zn, Cu, Ni, Mo)

 If a plant doesn’t have the minerals it needs, it is deficient.  Symptoms include:  Yellow leaves  Decreased chlorophyll  Red leaves  Shriveled or wrinkled leaves

 Topsoil is a mixture of particles derived from rocks, living organisms and humus (the remains of partially decayed organic materials)  Loam is the most fertile soil, made of sand and silt, and little amounts of clay

 Soil is made of both organic components, minerals, and living organisms.  It takes many centuries of decomposition for soil to become fertile  Agriculture naturally depletes soil quality  Crops must be rotated to restore minerals

 Fertilizers usually contain N-P-K in a ratio  Manure, compost, and dead fish are good fertilizers  Chemical fertilizers produce pollution, are not retained by the soil, and must be reapplied constantly

 pH affects whether or not plants can absorb minerals and ions  Every plant has a different pH need, but most prefer soil that is neutral or slightly basic

 80% of our atmosphere is N 2, which plants can’t use  Nitrogen fixing bacteria converts N 2 to NH 4 + and NO 3 -  The most important bacteria is called Rhizobium bacteria, which lives in little swellings in plant roots called nodules

 Epiphytes nourish themselves but grow on a another plant (ferns, orchids)  Parasitic plants absorb sugar and minerals from their living hosts (mistletoe)  Carnivorous Plants are photosynthetic but obtain nitrogen by killing and digesting insects (Venus flytrap, pitcher plants)

Chapter 38

 Pollen from stamen travels down the pollen tube of the carpel and fertilizes an egg  Zygote (2n) forms, divides into embryo, forms fruit  Fruits have seeds (developed from ovules)  Seed is dispersed, germinates, makes a new plant

 1. Pollen sacs (microsporangium) contain diploid microsporocytes  2. Each microsporocytes divides by meiosis to produce 4 haploid microspores, each develops into a pollen grain  3. A pollen grain matures when its nucleus divides in two and forms two sperm (this happens after it lands on the stigma)  4. Then it grows a pollen tube so the sperm can swim down to fertilize the egg

 1. Within the ovule’s megasporangium is a large diploid megasporocyte  2. The megasporocyte divides by meiosis and makes 4 haploid cells, but only one survives to become and megaspore  3. The megaspore divides 3 times, to form the embryo sac, a multicellular female gametophyte. This is the ovule.

 Some flowers, like garden peas, self-fertilize  Most flowers prevent self-fertilization:  Some have separate male and female flowers  Male and female parts might mature at different times  Plants can reject their own pollen

 1. A pollen grain lands on the stigma, and grows a pollen tube down the style towards the ovary  2. The pollen tube squirts out two sperm  3. One sperm fertilizes the egg, forming the zygote.  4. The other sperm combines with 2 of the polar nuclei (the eggs that didn’t survive) to become the endosperm (the food for the seed)

 The embryo goes through mitosis to form a seed.  A seed has a coat, an endosperm (food), cotyledons (baby leaves), shoots, and roots

 While the seeds are developing from ovules, the ovary of the flower is developing into a fruit.  There are 3 fruit types:  Simple: develop from a single carpel of one flower (pea pod)  Aggregate: develops from many carpels of one flower (raspberries)  Multiple: develops from many carpels of many flowers (pineapple)

 Seeds can remain dormant until conditions are right for germination  Germination starts with water uptake called imbibition.  The first organ to emerge is the root (from the radicle)  Next the shoot breaks through the soil surface

 Plants can clone themselves through asexual reproduction  Fragmentation is the separation of a parent plant into parts that develop into new plants  Dandelions can produce seeds without pollination (apomixis)  You can make clones from plant cuttings in your house  Grafting is attaching the stem of one plant to the roots of another