As a follow on to the “Teaming with Microbes” book, I decided to dive in more to learn about the biology behind the plants. And lots of biology I’ve got. First, the book is simply beautifully done; it’s made of glossy paper with lots of pictures and diagrams to back up the science. However, the science was over my head. Honestly, I read this book for a week to help with my jet lag during my travel to Asia – it was very effective in putting me to sleep when I couldn’t fall asleep due to the time zone shift. Nevertheless, I did learn something from it. Mainly, the plant is full of miracle of life: the cells, the DNA, and survival mechanism. The theme is the same for all the living things on earth; plants are equipped with the “magic” recipes to sustain themselves and to thrive. The general recipes are described in great details in this book.
The first three chapters are the most difficult barrier to finishing the book because it involves the science and biology of plants and gets pretty boring. Many times I wanted to put down the book and forget about it. But I kept going perhaps because I needed the sleep. I’m not sure if one must go through the first 3 chapters to learn about how the plants consume/digest the nutrients but I suppose they do pave the foundation for later chapters. The rewards were at the end – how to use the fertilizers to provide the nutrients and why. Most of the gardening books would not be able to explain why. But this book achieves its objectives of educating the readers what the plants eat and why. For occasional gardeners this book is not necessary, but for the hard core gardeners who are interested in knowing the biology behind seemingly benign gardening without taking on an agriculture degree this book serves well.
A summary of the book is as follows:
The book starts with the smallest element of the plant – the plant cell. A lot of people learned about this in middle school. I probably did but I either forgot about it or learned in Chinese that are no long retained.
The key structures of the cell: cell wall, aquaporin (protein that assists water transport), cytoplasm (all the stuff inside the plant cell except the nucleus), mitochondria (“power generator” that produces energy from the sugar made from photosynthesis), chloroplasts (one of the 3 plastids, “solar cell” absorbs light then converts CO2 and H2O into sugars and startch), robosomes (sites where messenger RNA sequences are read and proteins are synthesized), Golgi Apparatus (where the final packaging is done, and then molecules are shipped out in vesicles).
Chapter 2 covers the basic chemistry; lots of chemical reactions happen in the plant cells, mostly, exchanging of electrons. Oxidation loses electrons; reduction gains electrons. ATP serves as the currency of energy in plant cells to link chains of molecules during synthesis, makes proteins change shape, break apart water. Enzymes are protein catalysts that increase or decrease the rate of chemical reaction. Diffusion (high concentration to low concentration) and osmosis (diffusion of water: movement of water from low solutes to high solutes) vs. active transport (moved against concentration gradient, which requires energy).
Chapter 3 contains the science behind the plant nutrition. 4 groups of plant cells: meristemic (generic, undifferentiated), vascular (“plumbing pipes” composed of xylem, transports water and nutrients from the root, and phloem, transports water and sugars and others produced by a plant up and down the plant), dermal (provides protection to outer surfaces of a plant, a specialized dermal cells is the root hairs), ground (makes up the bulk of the plant body). Stomata are leaf pores that let in CO2 and let out H2O (evaporation of which is what draws water in). Plants form symbiotic relationships with specialized nitrogen-fixing bacteria and mycorrhizal fungi – partnerships are key for the uptake of nutrients by plants. Why does water enter the plant? Osmosis: more nutrient concentration inside the plant than outside. Sap flows through the phloem to the roots where sugars are stored for the winter. In the spring these stored sap nutrients move from the roots up through xylem. Two parts to the dermal tissue: epidermis (in plants) and periderm (in woody plants or trees). A typical leaf is comprised of the leaf blade or lamina, the petiole (the stalk that attaches the leaf to the stem), leaf axial.
Root cap cells help build the mucilage that lubricates the root and the soil. Mucilage is the mixture of sloughed off root tip cells, exudates from root tips and microbial populations and by-products. It has a great influence on the uptake of metal nutrients like phosphorus, zinc, iron and magnesium.
Chapter 4 covers the nutrients: Macronutrients (needed the greatest amount) mostly carbon dioxide, water (96%) and obtained in mineral form: nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Micronutrients (needed only trace amounts) obtained from the soil such as boron, chlorine, copper, iron, manganese, zinc, molybdenum, and nickle. Only 17 elements are needed to sustain life including ours. Nitrogen is the backbone of amino acids, the structural building blocks of proteins. No nitrogen, no proteins. 78% of atmosphere is made of Nitrogen but not usable by plants. Nitrogen-fixing organisms, diazotrophs, like Rhizobia and Frankia, which converts ammonia (NH4+) from decomposed organic materials to nitrite (NO2-) and then nitrate (NO3-). See the nitrogen cycle (from Wikipedia) below:
Mobility of nutrients: nitrogen, potassium, calcium, and magnesium are more mobile than copper, iron, manganese, nickel, and zinc. Deficiencies of mobile nutrients within plants tend to show symptoms in older leaves, whereas newer leaves and growing tips show signs of deficiencies in less mobile or immobile nutrients.
Chapter 5: Water movement: apoplastic pathway (porous space between the cellulose fibers of cell walls that allows water to travel into a plant without actually entering any cells) and simplastic pathway (guarded by the plasmalemma, which regulates what can enter a cell). Much of this chapter has been repeated from previous ones.
Chapter 6: Nutrient movement through plants. 4 methods of getting nutrients to the root: interception (accidental contacts), mass flow (sponge effect of the root, especially for nitrate), and diffusion (nutrients ions move toward the low-concentration near root), mocrobial partners such as mycorrhizal fungi (seduced by the root exudates of lipids, and carbon-based molecules. Active and passive transport methods to get through the cell membrane barrier. Calcium, sodium, magnesium, aplant-made sugar, and hydrogen ions are all actively transported. Transport protein: channel membrane proteins (tunnel, no energy used) and carrier membrane proteins (requires substances to bind to hem for their movement across the membrane, like enzymes), protein pumps (proton pumps or ATPases). Once inside the plant, nutrients move with water as a result of transpiration. They follow the symplastic or apoplastic pathway until they enter the xylem and are transported up and throughout the plant.
Chapter 7: the molecules of life (the end synthesized products of the nutrients): carbohydrates (glucose: monomer, fuctose, maltose, polysaccharide or starch), proteins (made of carbon, oxygen, hydrogen and nitrogen – amino acids up to 20 types. Make up cells. Enzymes are made by linking mino acids in specific orders), lipids (stores energy – 9 categories of fatty acids: fats, oils, waxes, glycolipids, phospholipids, lipoproteins, steroids, terpenes, and carotenoids) , and nucleic acids (DNA and RNA enables life to replicates itself).
Chapter 8: Soil testing. Use fertilizers based on information obtained by soil testing.
Chapter 9: Factors influencing nutrient availabilities: temperature, pH levels (soil locks up certain nutrients in certain pH range, see lock up charge below from this source), soil aeration, mineral and organic composition (affects the electric charges), soil moisture.
Chapter 10: what and when to feed plants: Natural Nitrogen Fertilizers: bat guando, blood meal, corn gluten meal, feather meal, fish emulsion, fish meal, fish powder, hydrolyzed fish, soy bean meal, chilean nitrate, human hair and urine. Phosphorous fertilizer: bone meal, bad guano, colloidal rock phosphate, and crab shell meal. Potassium: greensand, wood ashes, and sulfate of potash. Calcium: Calcitic limestone, and dolomitic limestone. Micronutrients: shrimp shell meal, kelp meal, kelp powder, and liquid kelp. Biofertilizers: Rhizobia and Frankia (bacteria), Azotobacter and Azospirillum, phosphate-solubilizing bacteria and fungi, mycorrhizal fungi, comopost, earthworm castings, and manures.