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Marijuana Botany by Robert Connel Clark
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<blockquote data-quote="cannebosanac" data-source="post: 20017" data-attributes="member: 1357"><p>poglavlje 2 nastavak</p><p></p><p>Many synthetic compounds have been shown to have </p><p>auxin activity and are commercially available, such as </p><p>napthaleneacetic acid (NAA), indolebutyric acid (IBA), </p><p>and 2,4-dichlorophenoxyacetic acid (2,4 DPA), but only </p><p>indoleacetic acid has been isolated from plants. Naturally </p><p>occurring auxin is formed mainly in the apical shoot men- </p><p>stem and young leaves. It moves downward after its forma- </p><p>tion at the growing shoot tip, but massive concentrations </p><p>of auxins in rooting solutions will force travel up the vas- </p><p>cular tissue. Knowledge of the physiology of auxins has </p><p>led to practical applications in rooting cuttings. It was </p><p>shown originally by Went and later by Thimann and Went </p><p>that auxins promote adventitious root formation in stem </p><p>cuttings. Since application of natural or synthetic auxin </p><p>seems to stimulate adventitious root formation in many </p><p>plants, it is assumed that auxin levels are associated with </p><p>the formation of root initials. Further research by Warmke </p><p>and Warmke (1950) suggested that the levels of auxin </p><p>may determine whether adventitious roots or shoots are </p><p>formed, with high auxin levels promoting root growth and </p><p>low levels favoring shoots. </p><p>Cytokinins are chemical compounds that stimulate </p><p>cell growth. In stem cuttings, cytokinins suppress root </p><p>growth and stimulate bud growth. This is the opposite of </p><p>the reaction caused by auxins, suggesting that a natural </p><p>balance of the two may be responsible for regulating nor- </p><p>mal plant growth. Skoog discusses the use of solutions </p><p>of equal concentrations of auxins and cytokinins to pro- </p><p>mote the growth of undifferentiated callus tissues. This </p><p>may provide a handy source of undifferentiated material </p><p>for cellular cloning. </p><p>Although Cannabis cuttings and layers root easily, </p><p>variations in rootability exist and old stems may resist </p><p>rooting. Selection of rooting material is highly important. </p><p>Young, firm, vegetative shoots, 3 to 7 millimeters (1/8 to </p><p>1/4 inch) in diameter, root most easily. Weak, unhealthy </p><p>plants are avoided, along with large woody branches and </p><p>reproductive tissues, since these are slower to root. Stems </p><p>of high carbohydrate content root most easily. Firmness is </p><p>a sign of high carbohydrate levels in stems but may be con- </p><p>fused with older woody tissue. An accurate method of de- </p><p>termining the carbohydrate content of cuttings is the </p><p>iodine starch test. The freshly cut ends of a bundle of </p><p>cuttings are immersed in a weak solution of iodine in </p><p>potassium iodide. Cuttings containing the highest starch </p><p>content stain the darkest; the samples are rinsed and sorted </p><p>accordingly. High nitrogen content cuttings seem to root </p><p>more poorly than cuttings with medium to low nitrogen </p><p>content. Therefore, young, rapidly-growing stems of high </p><p>nitrogen and low carbohydrate content root less well than </p><p>slightly older cuttings. For rooting, sections are selected </p><p>that have ceased elongating and are beginning radial growth. </p><p>Staminate plants have higher average levels of carbohydrates </p><p>than pistillate plants, while pistillate plants exhibit higher </p><p>nitrogen levels. It is unknown whether sex influences root- </p><p>ing, but cuttings from vegetative tissue are taken just after </p><p>sex determination while stems are still young. For rooting </p><p>cloning stock or parental plants, the favorable balance (low </p><p>nitrogen-to-high carbohydrate) is achieved in several ways: </p><p>1 - Reduction of the nitrogen supply will slow shoot </p><p>growth and allow time for carbohydrates to accumulate. </p><p>This can be accomplished by leaching (rinsing the soil with </p><p>large amounts of fresh water), withholding nitrogenous </p><p>fertilizer, and allowing stock plants to grow in full sun- </p><p>light. Crowding of roots reduces excessive vegetative </p><p>growth and allows for carbohydrate accumulation. </p><p>2 - Portions of the plant that are most likely to root </p><p>are selected. Lower branches that have ceased lateral </p><p>growth and begun to accumulate starch are the best. The </p><p>carbohydrate-to-nitrogen ratio rises as you move away </p><p>from the tip of the limb, so cuttings are not made too short. </p><p>3 - Etiolation is the growth of stem tissue in total </p><p>darkness to increase the possibility of root initiation. </p><p>Starch levels drop, strengthening tissues and fibers begin to </p><p>soften, cell wall thickness decreases, vascular tissue is </p><p>diminished, auxin levels rise, and undifferentiated tissue </p><p>begins to form. These conditions are very conducive to the </p><p>initiation of root growth. If the light cycle can be con- </p><p>trolled, whole plants can be subjected to etiolation, but </p><p>usually single limbs are selected for cloning and wrapped </p><p>for several inches just above the area where the cutting </p><p>will be taken. This is done two weeks prior to rooting. The </p><p>etiolated end may then be unwrapped and inserted into </p><p>the rooting medium. Various methods of layers and </p><p>cuttings rooted below soil level rely in part on the effects </p><p>of etiolation. </p><p>4 - Girdling a stem by cutting the phloem with a </p><p>knife or crushing it with a twisted wire may block the </p><p>downward mobility of carbohydrates and auxin and root- </p><p>ing cofactors, raising the concentration of these valuable </p><p>components of root initiation above the girdle. Making Cuttings </p><p>Cuttings of relatively young vegetative limbs 10 to 45 </p><p>centimeters (4 to 18 inches) are made with a sharp knife or </p><p>razor blade and immediately placed in a container of clean, </p><p>pure water so the cut ends are well covered. It is essential </p><p>that the cuttings be placed in water as soon as they are </p><p>removed or a bubble of air (embolism) may enter the cut </p><p>end and block the transpiration stream in the cutting, </p><p>causing it to wilt. Cuttings made under water avoid the </p><p>possibility of an embolism. If cuttings are exposed to the </p><p>air they are cut again before being inserted into the rooting </p><p>medium. </p><p>The medium should be warm and moist before cut- </p><p>tings are removed from the parental plant. Rows of holes </p><p>are made in the rooting medium with a tapered stick, </p><p>slightly larger in diameter than the cutting, leaving at least </p><p>10 centimeters (4 inches) between each hole. The cuttings </p><p>are removed from the water, the end to be rooted treated </p><p>with growth regulators and fungicides (such as Rootone F </p><p>or Hormex), and each cutting placed in its hole. The cut </p><p>end of the shoot is kept at least 10 centimeters (4 inches) </p><p>from the bottom of the medium. The rooting medium is </p><p>lightly tamped around the cutting, taking care not to </p><p>scrape off the growth regulators. During the first few days </p><p>the cuttings are checked frequently to make sure every- </p><p>thing is working properly. The cuttings are then watered </p><p>with a mild nutrient solution once a day. </p><p>Hardening-off</p></blockquote><p></p>
[QUOTE="cannebosanac, post: 20017, member: 1357"] poglavlje 2 nastavak Many synthetic compounds have been shown to have auxin activity and are commercially available, such as napthaleneacetic acid (NAA), indolebutyric acid (IBA), and 2,4-dichlorophenoxyacetic acid (2,4 DPA), but only indoleacetic acid has been isolated from plants. Naturally occurring auxin is formed mainly in the apical shoot men- stem and young leaves. It moves downward after its forma- tion at the growing shoot tip, but massive concentrations of auxins in rooting solutions will force travel up the vas- cular tissue. Knowledge of the physiology of auxins has led to practical applications in rooting cuttings. It was shown originally by Went and later by Thimann and Went that auxins promote adventitious root formation in stem cuttings. Since application of natural or synthetic auxin seems to stimulate adventitious root formation in many plants, it is assumed that auxin levels are associated with the formation of root initials. Further research by Warmke and Warmke (1950) suggested that the levels of auxin may determine whether adventitious roots or shoots are formed, with high auxin levels promoting root growth and low levels favoring shoots. Cytokinins are chemical compounds that stimulate cell growth. In stem cuttings, cytokinins suppress root growth and stimulate bud growth. This is the opposite of the reaction caused by auxins, suggesting that a natural balance of the two may be responsible for regulating nor- mal plant growth. Skoog discusses the use of solutions of equal concentrations of auxins and cytokinins to pro- mote the growth of undifferentiated callus tissues. This may provide a handy source of undifferentiated material for cellular cloning. Although Cannabis cuttings and layers root easily, variations in rootability exist and old stems may resist rooting. Selection of rooting material is highly important. Young, firm, vegetative shoots, 3 to 7 millimeters (1/8 to 1/4 inch) in diameter, root most easily. Weak, unhealthy plants are avoided, along with large woody branches and reproductive tissues, since these are slower to root. Stems of high carbohydrate content root most easily. Firmness is a sign of high carbohydrate levels in stems but may be con- fused with older woody tissue. An accurate method of de- termining the carbohydrate content of cuttings is the iodine starch test. The freshly cut ends of a bundle of cuttings are immersed in a weak solution of iodine in potassium iodide. Cuttings containing the highest starch content stain the darkest; the samples are rinsed and sorted accordingly. High nitrogen content cuttings seem to root more poorly than cuttings with medium to low nitrogen content. Therefore, young, rapidly-growing stems of high nitrogen and low carbohydrate content root less well than slightly older cuttings. For rooting, sections are selected that have ceased elongating and are beginning radial growth. Staminate plants have higher average levels of carbohydrates than pistillate plants, while pistillate plants exhibit higher nitrogen levels. It is unknown whether sex influences root- ing, but cuttings from vegetative tissue are taken just after sex determination while stems are still young. For rooting cloning stock or parental plants, the favorable balance (low nitrogen-to-high carbohydrate) is achieved in several ways: 1 - Reduction of the nitrogen supply will slow shoot growth and allow time for carbohydrates to accumulate. This can be accomplished by leaching (rinsing the soil with large amounts of fresh water), withholding nitrogenous fertilizer, and allowing stock plants to grow in full sun- light. Crowding of roots reduces excessive vegetative growth and allows for carbohydrate accumulation. 2 - Portions of the plant that are most likely to root are selected. Lower branches that have ceased lateral growth and begun to accumulate starch are the best. The carbohydrate-to-nitrogen ratio rises as you move away from the tip of the limb, so cuttings are not made too short. 3 - Etiolation is the growth of stem tissue in total darkness to increase the possibility of root initiation. Starch levels drop, strengthening tissues and fibers begin to soften, cell wall thickness decreases, vascular tissue is diminished, auxin levels rise, and undifferentiated tissue begins to form. These conditions are very conducive to the initiation of root growth. If the light cycle can be con- trolled, whole plants can be subjected to etiolation, but usually single limbs are selected for cloning and wrapped for several inches just above the area where the cutting will be taken. This is done two weeks prior to rooting. The etiolated end may then be unwrapped and inserted into the rooting medium. Various methods of layers and cuttings rooted below soil level rely in part on the effects of etiolation. 4 - Girdling a stem by cutting the phloem with a knife or crushing it with a twisted wire may block the downward mobility of carbohydrates and auxin and root- ing cofactors, raising the concentration of these valuable components of root initiation above the girdle. Making Cuttings Cuttings of relatively young vegetative limbs 10 to 45 centimeters (4 to 18 inches) are made with a sharp knife or razor blade and immediately placed in a container of clean, pure water so the cut ends are well covered. It is essential that the cuttings be placed in water as soon as they are removed or a bubble of air (embolism) may enter the cut end and block the transpiration stream in the cutting, causing it to wilt. Cuttings made under water avoid the possibility of an embolism. If cuttings are exposed to the air they are cut again before being inserted into the rooting medium. The medium should be warm and moist before cut- tings are removed from the parental plant. Rows of holes are made in the rooting medium with a tapered stick, slightly larger in diameter than the cutting, leaving at least 10 centimeters (4 inches) between each hole. The cuttings are removed from the water, the end to be rooted treated with growth regulators and fungicides (such as Rootone F or Hormex), and each cutting placed in its hole. The cut end of the shoot is kept at least 10 centimeters (4 inches) from the bottom of the medium. The rooting medium is lightly tamped around the cutting, taking care not to scrape off the growth regulators. During the first few days the cuttings are checked frequently to make sure every- thing is working properly. The cuttings are then watered with a mild nutrient solution once a day. Hardening-off [/QUOTE]
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