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Plant Physiology Morphology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization.

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Presentation on theme: "Plant Physiology Morphology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization."— Presentation transcript:

1 Plant Physiology Morphology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization Carbohydrates and Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients Life Cycles and Phenology

2 Seasonality and Life Cycles Terminology Life Cycles Seasonal growth rates Forage Quality RDM Seasonality and Life Cycles Seasonal Growth Rates You are here Forage Quality RDM Life Cycles and Phenology

3 The Phenology Handbook, pg 1-15 George et al Annual Range Forage Production George and Bell Using Stage of Maturity…….. Return to Course Map Seasonality and Seasonality and Life Cycles Life Cycles SEASONALITY & LIFE CYCLES

4 Terminology Terminology Life Cycles Forage Quality Seasonal growth rates RDM Return to Course Map Plant Physiology

5 Annual Perennial Seasonality and Life Cycles Return to Course Map

6 Grass: monocot, most are not woody Forb: dicot, non-woody Shrub Dicot, woody Return to Course Map Seasonality and Life Cycles

7 Return to Course Map Seasonality and Life Cycles PHENOLOGY PHENOLOGY is the science that measures the timing of life cycle events for plants, animals, and microbes, and detects how the environment influences the timing of those events. In the case of flowering plants, these life cycle events, include leaf budburst, first flower, last flower, first ripe fruit, seed set, leaf shedding, others.

8 Terminology Life Cycles Life Cycles Forage Quality Seasonal growth rates RDM Return to Course Map Plant Physiology

9 Return to Course Map Seasonality and Life Cycles

10 Annuals Germination Vegetative Seedling establishment Leaf growth Winter growth is slow Growth accelerates in spring Flowering Seed Set, Drying Dry and Die Seasonality and Life Cycles Return to Course Map

11 NDJFMAMJJASO Germination & Seedling Establishment Slow Vegetative Growth Rapid Vegetative Growth Little or No Vegetative Growth Tiller Development Flowering Seed Development Seed Set Drying Stems & Leaves Dry & Dead Stems & Leaves Seasonality and Life Cycles Timing of phenological events

12 Perennials Lives several years Sexual reproduction Vegetative reproduction Stolons and Rhizomes Winter dormancy Dry season dormancy Vegetative phase Flowering Seed set and dispersal Dormancy Return to Course Map Seasonality and Life Cycles

13 Return to Course Map NDJFMAMJJASO Dormant or Slow Vegetative GrowthRapid Vegetative Growth Slow Vegetative Growth DormantTiller Development DormantCarbohydrate UseCarbohydrate Storage Apical Meristems Near Soil Surface Flower Stems Elongate Flowering Seed Development Seed Set Drying Stems & Leaves Dry & Dead Stems & Leaves Seasonality and Life Cycles Timing of phenological events

14 Return to Course Map Seasonality and Life Cycles Phenological events

15 Terminology Life Cycles Forage Quality Forage Quality Seasonal growth rates RDM Return to Course Map Plant Physiology

16 Crude protein decreases in annual grasses with stage of maturity (see ANR Publications 8019 and 8022) Return to Course Map Seasonality and Life Cycles

17 Terminology Life Cycles Forage Quality Seasonal growth rates Seasonal growth rates RDM Return to Course Map Plant Physiology

18 D1 J1 F1 M1 A1 M1 Peak Return to Course Map Seasonality and Life Cycles

19 Growth rates of perennials in northeastern California Return to Course Map Seasonality and Life Cycles

20 Terminology Life Cycles Seasonal growth rates Forage Quality RDM RDM Return to Course Map Plant Physiology

21 Moderate grazing results in recommended RDM levels Heavy grazing results in low RDM levels Light grazing results in high RDM levels Seasonality and Life Cycles Return to Course Map

22 Seasonality and Life Cycles Return to Course Map In this section you have learned the differences between annual and perennial life cycles and how plant growth rates and forage quality change as range and pasture plants move through their life cycle.

23 Plant Physiology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization Carbohydrates and Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients Life Cycles and Phenology Morphology

24 Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction You are here Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy Morphology and Development

25 Briske, Chp 4. Dev. Morph and Phys of Grasses. Introduction and Developmental Morphology Sections. Skinner and Moore. Growth and Dev of Forage Plants How Grass Grows MORPHOLOGY

26 Grass Anatomy Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction Return to Course Map Plant Physiology

27 Please review How Grass Grows at the link below. Overview of the Grass Plant Shoot Development Crown Leaf Formation Leaf Expansion Dynamics Tillering Rhizome and Stolon Development Flowering Root Development Germination Process Seasonal Development Return to Course Map Morphology and Development

28 Apical meristems (flower) Axillary buds (give rise to tillers, rhizomes and stolons) Intercalary meristems or collar (leaf expansion) Some growing points become elevated as the growing season progresses. Buds near the ground are less likely to be grazed Delaying bud elevation reduces risk of bud removal by grazing Return to Course Map Morphology and Development

29 Apical meristems (flower) Axillary buds (give rise to tillers, rhizomes and stolons) Intercalary meristems or collar (leaf expansion) Some growing points become elevated as the growing season progresses. Buds near the ground are less likely to be grazed Delaying bud elevation reduces risk of bud removal by grazing Return to Course Map Morphology and Development

30 Apical meristems (flower) Axillary buds (give rise to tillers, rhizomes and stolons) Intercalary meristems or collar (leaf expansion) Some growing points become elevated as the growing season progresses. Buds near the ground are less likely to be grazed Delaying bud elevation reduces risk of bud removal by grazing Return to Course Map Morphology and Development

31 Apical meristems (flower) Axillary buds (give rise to tillers, rhizomes and stolons) Intercalary meristems or collar (leaf expansion) Some growing points become elevated as the growing season progresses. Buds near the ground are less likely to be grazed Delaying bud elevation reduces risk of bud removal by grazing Apical meristem rising Return to Course Map Morphology and Development

32 In the vegetative phase, shoots consist predominantly of leaf blades. Leaf blade collars remain nested in the base of the shoot and there is no evidence of sheath elongation or culm development. Return to Course Map Morphology and Development

33 Floral induction - Apical meristems is gradually converted from a vegetative bud to a floral bud. During the transition phase, leaf sheaths begin to elongate, raising the meristematic collar zone to a grazable height. Culm internodes also begin elongation in an "un-telescoping" manner beginning with the lowermost internode thereby raising the meristematic zone (floral bud and leaf bases) to a vulnerable position. Return to Course Map Morphology and Development

34 The flowering phase begins with the conversion from vegetative to floral bud. Much of this is unseen until the emergence of the seed head from the sheath of the flag leaf (boot stage). Within a few days, individual florets within the seed head are ready for pollination. Apical meristem rising Return to Course Map Morphology and Development

35 Grass Anatomy Forb Anatomy Forb Anatomy Shrub Anatomy Reproduction Return to Course Map Plant Physiology

36 Return to Course Map Morphology and Development

37 Return to Course Map Growing point or apical bud Morphology and Development

38 Grass Anatomy Forb Anatomy Shrub Anatomy Shrub Anatomy Reproduction Return to Course Map Plant Physiology

39 Coast live oak resprouts Chamise resprouts Return to Course Map Morphology and Development

40 Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction Reproduction Return to Course Map Plant Physiology

41 Long Day Plants Short Day Plants Sexual Reproduction (flowers and seeds) Vegetative Reproduction (stolons, rhizomes) Return to Course Map Morphology and Development

42 Some plants are long-day plants and others are short-day plants. The long-day plants reach the flowering phenological stage after exposure to a critical photoperiod and during the period of increasing daylight between mid April and mid June. Generally, most cool-season plants with the C 3 photosynthetic pathway are long-day plants and reach flower phenophase before 21 June. Return to Course Map Morphology and Development

43 Short-day plants are induced into flowering by day lengths that are shorter than a critical length and that occur during the period of decreasing day length after mid June. Short-day plants are technically responding to the increase in the length of the night period rather than to the decrease in day length. Generally, most warm-season plants with the C 4 photosynthetic pathway are short-day plants and reach flower phenophase after 21 June. The annual pattern in the change in daylight duration follows the calendar and is the same every year for each region. Return to Course Map Morphology and Development

44 Plant populations persist through both asexual (vegetative) reproduction and sexual reproduction. The frequency of true seedlings produced from seed is low in established grasslands and occurs only during years with favorable moisture and temperature conditions in areas of reduced competition from older tillers, and when resources are easily available to the growing seedling. Return to Course Map Morphology and Development

45 Sexual reproduction is necessary for a population to maintain the genetic diversity enabling it to withstand large-scale changes. However, production of viable seed each year is not necessary to the perpetuation of a healthy grassland. Return to Course Map Morphology and Development SEXUAL

46 Reproductive shoots are adapted for seed production rather than for tolerance to defoliation Grass species that produce a high proportion of reproductive shoots are less resistant to grazing than are those species in which a high proportion of the shoots remains vegetative. Return to Course Map Morphology and Development SEXUAL

47 Vegetative growth is the dominant form of reproduction in semiarid and mesic grasslands Annual plants are dependent on seed production each year for survival. Short-lived perennials depend on seed production. Long-lived perennials rely more on vegetative reproduction. Return to Course Map Morphology and Development ASEXUAL OR VEGETATIVE

48 Morphology and Development

49 Bunch grasses spread by the production of tillers. Stoloniferous grasses spread by lateral stems, called stolons, that creep over the ground and give rise to new shoots periodically along the length of the stolon. Rhizomatous grasses spread from below ground stems known as rhizomes. Return to Course Map Morphology and Development ASEXUAL OR VEGETATIVE

50 . Return to Course Map Morphology and Development In this section you learned about plant growing points, how plants grow, phases of plant growth and reproduction. You learned that vegetative reproduction in the form of tillers, stolons and rhizomes are more important than reproduction via seeds in most grasslands. You also learned that buds close to the ground are less vulnerable to grazing than when they are elevated.

51 Plant Physiology Morphology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization Carbohydrates and Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients Life Cycles and Phenology

52 Plant Physiology Germination & Seedling Establishment Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Plant Physiology Germination and Seedling Establishment Carbohydrates and Allocation Secondary Compounds Photosynthesis Water and Nutrients

53 McKell, C.M Morphogenesis and management of annual range plants in the United States. Pg Briske, Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section. Waller and Lewis Occurrence of C3 and C4 photosynthetic pathways in North American grasses. Carbohydrate Reserves: What you learned may be wrong.

54 Germination and Seedling Establishment Germination and Seedling Establishment Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Return to Course Map Plant Physiology

55 Return to Course Map Plant Physiology

56 See Anatomy Embryo Endosperm (food reserves) Seed coat (pericarp) Variable seed production Empty seeds Empty Seeds Seed Coat Return to Course Map Plant Physiology

57 Return to Course Map Plant Physiology

58 Return to Course Map Plant Physiology

59 Oxygen is required for respiration during germination. Oxygen is found in soil pore spaces but if a seed is buried too deeply within the soil or the soil is waterlogged, the seed can be oxygen starved. Some seeds have impermeable seed coats sometimes called hard seed. Hard seed is common in legumes Return to Course Map Plant Physiology

60 Temperature also influences germination. Seeds from different species and even seeds from the same plant germinate over a wide range of temperatures. Seeds often have a temperature range within which they will germinate, and they will not do so above or below this range. Return to Course Map Plant Physiology

61 Some seeds require exposure to cold temperatures (vernalization) to break dormancy. Seeds in a dormant state will not germinate even if conditions are favorable. Some seeds will only germinate following hot weather and others exposed to hot temperatures during a forest fire which cracks their seed coats. Some seeds need to pass through an animal's digestive tract to weaken the seed coat enough to allow the seedling to emerge. Return to Course Map Plant Physiology

62 Variability in the rate of germination exists between and within species. Seed size has been shown to be a critical factor in promoting seedling vigor. In legumes and other forbs, seed coat hardness or impermeability often retards germination but spreads germination over years which is a survival advantage for the species. Return to Course Map Plant Physiology

63 On annual rangelands estimates of germinable seed exceed 20,000 per m 2. On annual rangelands the number of plants early in the growing season has been reported to vary from 20 to nearly 100 per square inch. Considerable reduction in this number takes place as the season progresses. The lost seedlings decay and provide a flush of nutrients early in the growing season. Return to Course Map Plant Physiology

64 Rapid root growth is fundamental to establishment and development of annual rangeland plants. Individual plants and species may gain an advantage over competitors if they exhibit rapid root growth and are able to maintain both rapid root and top growth. Annual grasses frequently exhibit root growth rates greater than native perennial grasses Annual grass (cheatgrass) roots (b) grew faster in this study than blue bunch wheatgrass (native perennial ) roots (a) (Harris 1977, JRM) Return to Course Map Plant Physiology

65 Germination and Seedling Establishment Photosynthesis Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Return to Course Map Plant Physiology

66 CH 2 O + O 2 Sunlight Chlorophyll Return to Course Map Plant Physiology

67 Plants are the only source of energy for grazing animals. The formation of sugars, starches, proteins and other foods is dependent on photosynthesis. Plants do not get food from the soil. They obtain raw materials needed for photosynthesis and subsequent food production When leaves are removed from plants, food-producing capacity is reduced. Return to Course Map Plant Physiology

68 Return to Course Map To learn more about Photosynthesis: ER17M Plant Physiology

69 4.Physiological efficiency 5.Soil nutrients 6.Water supply 7.Temperature Factors that influence photosynthetic rate 1.Leaf area 2.Light intensity and quality 3.CO 2 content of the air Return to Course Map Plant Physiology

70 Relationship between light interception and leaf area (Brougham 1956) Return to Course Map Plant Physiology

71 Return to Course Map Lightly grazed Closely grazed Plant Physiology

72 (Parsons et al. 1983) Return to Course Map Plant Physiology

73 Relationship between leaf area and herbage yield (Brougham 1956) Return to Course Map Plant Physiology

74 NPP=GPP - R GPP and NPP increase as leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP Return to Course Map Plant Physiology

75 Guard Cells Stomate Return to Course Map Plant Physiology

76 Water required for photosynthesis Lost through stomates (transpiration) Arid and semi-arid lands frequently subjected to water stress Drought tolerant Return to Course Map Plant Physiology

77 Return to Course Map Plant Physiology C3, C4 & CAM Pathways

78 C3 because CO 2 is first incorporated into a 3-carbon compound. Stomata are open during the day. Photosynthesis takes place throughout the leaf. Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and, under normal light conditions. Most plants are C3. Return to Course Map Plant Physiology

79 CO 2 is first incorporated into a 4-carbon compound Stomata are open during the day. Photosynthesis takes place in inner bundle sheath cells Adaptive Value: Photosynthesizes faster than C3 plants under high light intensity and high temperatures. Better water use efficiency than C3 because CO2 uptake is faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis C4 plants include several thousand species in at least 19 plant families Examples: fourwing saltbush, corn, and many summer annual plants Return to Course Map Plant Physiology

80 Crassulacean Acid Metabolism (CAM) Stomata open at night and are usually closed during the day. The CO2 is converted to an acid and stored during the night. During the day, the acid is broken down and the CO2 is released for photosynthesis Adaptive Value: Better Water Use Efficiency than C3 plants CAM-Idle When conditions are extremely arid, CAM plants can just leave their stomata closed night and day. CAM plants include many succulents such as cactuses and agaves and also some orchids and bromeliadscactuses Return to Course Map Plant Physiology

81 Return to Course Map Plant Physiology Waller, S.S. and J.K. Lewis Occurrence of C3 and C4 Photosynthetic Pathways in North American Grasses. Journal of Range Management 32:12-28 for an review and list of C3 and C4 range plants.

82 Return to Course Map Plant Physiology

83 Return to Course Map Plant Physiology C3 VS C4

84 Return to Course Map Plant Physiology

85 Return to Course Map Plant Physiology C3 VS C4:

86 Germination and Seedling Establishment Photosynthesis Carbohydrates and Carbohydrate Allocation Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Return to Course Map Plant Physiology

87 Carbohydrates are the plants energy source Energy needed for: Root replacement Leaf and stem growth following dormancy Respiration during dormancy Bud formation Regrowth following top removal Return to Course Map Plant Physiology

88 Return to Course Map Plant Physiology

89 Return to Course Map Plant Physiology

90 Return to Course Map Plant Physiology

91 Return to Course Map Plant Physiology

92 Germination and Seedling Establishment Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Water and Nutrients Secondary Compounds Return to Course Map Plant Physiology

93 Return to Course Map Plant Physiology For more information on plant water movement see these two videos:

94 Return to Course Map Plant Physiology

95 Return to Course Map Plant Physiology

96 Return to Course Map Plant Physiology

97 Germination and Seedling Establishment Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Secondary Compounds Return to Course Map Plant Physiology

98 Return to Course Map Plant Physiology Many secondary compounds are toxic to livestock and humans. For more information see Livestock-Poisoning Plants of California.Livestock-Poisoning Plants of California

99 Conifers accumulate monoterpenes Return to Course Map Plant Physiology TERPENES

100 Lignin Flavenoids Tannin isoflavenoids in legumes Tannins in oak leaves Return to Course Map Plant Physiology PHENOLICS

101 Alkaloids Cynanogenic glycosides Return to Course Map Plant Physiology NITROGEN CONTAINING COMPOUNDS

102 Return to Course Map Plant Physiology ALLELOPATHY

103 Return to Course Map Plant Physiology In the plant physiology section you learned about germination and seedling establishment, photosynthesis, carbohydrate storage and allocation, plant water relations and nutrient uptake and secondary compounds. You learned that fire and heat can influence germination along with soil moisture and temperature. You also learned that photosynthetic rate increases with leaf area to some optimum level and then slows with continued increases in leaf area. You learned about three photosynthetic pathways (C3, C4 and CAM) and their adaptive value. You learned that carbohydrates produced during photosynthesis are used for plant growth or stored to meet future needs. And finally you learned about secondary compounds

104 Plant Physiology Morphology Seasonality and Life Cycles Grazing and Plant Growth Seasonal Growth Rates Germination and Seedling Establishment Grazing Optimization Carbohydrates and Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients Life Cycles and Phenology

105 Grazing and Plant Growth Grazing Effects Grazing Optimization Grazing Resistance Grazing and Plant Growth Grazing Optimization Grazing Resistance Grazing Effects

106 Briske, Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section. Trlica, J Grass Growth and Response to Grazing. A quick lesson in plant structure, growth and regrowth for pasture-based dairy systems. Noy-Meir, I Compensating growth of grazed plants and its relevance to the use of rangelands.

107 Grazing Effects Grazing Effects Grazing Optimization Grazing Resistance Return to Course Map Grazing and Plant Growth

108 Detrimental Effects Growth Promoting Effects Return to Course Map Grazing and Plant Growth

109 Return to Course Map Grazing and Plant Growth Removal of photosynthetic tissue Reduced carbohydrate storage Reduced root growth Reduced seed production

110 Return to Course Map Grazing and Plant Growth 1.Grazing that is too heavy can reduce leaf area and reduce photosynthesis and carbohydrate production. Grazing can influence leaf area

111 Return to Course Map Grazing and Plant Growth 1.Heavy grazing can weaken root systems increasing moisture stress Grow leaves, stems, roots and buds. Return to Course Map

112 Grazing and Plant Growth 1.Heavy grazing can weaken root systems increasing moisture stress Leaves, stems, roots and other plant parts

113 Return to Course Map Grazing and Plant Growth Seed production

114 Return to Course Map Grazing and Plant Growth Carbohydrates are the plants energy source

115 Return to Course Map Grazing and Plant Growth Detrimental Effects Growth Promoting Effects

116 Return to Course Map Grazing and Plant Growth Increased photosynthesis Increased tillering Reduced shading Reduced transpiration

117 Return to Course Map Grazing and Plant Growth 1. Intensity 2. Timing 3. Frequency 4. Grazing of surrounding plants

118 Return to Course Map Grazing and Plant Growth 1. Decreases evapotranspiration 2. Moderates surface microclimate during germination and seedling establishment 3. Slows surface runoff and increases infiltration 4. Protects soil from erosion

119 Return to Course Map Grazing and Plant Growth Grazing too close reduces reserves and slows recovery following grazing

120 Return to Course Map Grazing and Plant Growth Plant A was allowed to grow for three months without clipping. Healthy root system Plant B was clipped to 3 inches every three weeks for 3 months. Healthy root system Plant C was clipped to 1 inch every week for 3 months. Very weak root system and might not survive a drought ACB Return to Course Map

121 Grazing and Plant Growth Heavy Grazing: Decreased photosynthesis Reduced carbohydrate storage Reduced root growth Reduced seed production Reduced ability to compete with ungrazed plants Reduce accumulation of litter or mulch which decreases water infiltration and retention, plus it protects soil from erosion. Light to Moderate Grazing: Increased plant productivity Increased tillering Reduced shading of lower leaves Reduced transpiration losses Reduced ability to compete with ungrazed plants Reduction of excessive litter or mulch that can physically or chemically inhibit vegetative growth. Excessive mulch promotes pathogens and insects that can damage forage plants. Negative effects of heavy grazing vs. possible effects of light to moderate grazing on range plant physiology

122 Return to Course Map Grazing and Plant Growth Grazing Effects Grazing Optimization Grazing Resistance

123 There are levels of grazing that can result in increased productivity G.O. is a complex and sometime controversial subject. Return to Course Map Grazing and Plant Growth

124 Return to Course Map Grazing and Plant Growth

125 Return to Course Map Grazing and Plant Growth NPP=GPP - R GPP and NPP increase as leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP

126 NPP=GPP - R GPP and NPP increase as leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP Grazing reduces leaf area G.O. says if grazing keeps LAI near 4, NPP is optimized. May occur in some species, more likely in pasture. Some species are extremely susceptible to grazing even at light intensities. Return to Course Map Grazing and Plant Growth

127 Return to Course Map Grazing and Plant Growth C = control no clipping TB = terminal bud removed only 60 = 60% current annual growth removed 100 = 100% current annual growth removed

128 Return to Course Map Grazing and Plant Growth

129 Return to Course Map Grazing and Plant Growth Herbivore-induced physiological processes Accelerated photosynthesis per unit leaf area Accelerated nutrient absorption per unit root mass Greater resource allocation to shoots Increased tiller initiation Improved water status Herbivore-mediated environmental modification Increased irradiance on remaining leaves and young tillers Conservation of soil water following leaf area removal Accelerated rate of nutrient cycling Increased activity of decomposer organisms

130 Return to Course Map Grazing and Plant Growth Grazing Effects Grazing Optimization Grazing Resistance

131 Return to Course Map Grazing and Plant Growth

132 Mechanical Biochemical Return to Course Map Grazing and Plant Growth

133 Return to Course Map Grazing and Plant Growth

134 Return to Course Map Grazing and Plant Growth PLANT PHYSIOLOGY Ability to regrow quickly following grazing Ability to compete for water and nutrients enable some plants to regrow more quickly In some plant grazing stimulates absorption of nutrients. However, in many species removal of leaves and stems decreases nutrient absorption. Ability to quickly move nutrients and carbohydrates between roots and shoots

135 Return to Course Map Grazing and Plant Growth Grasses Higher proportion of culmless (stemless) shoots than species with low resistance Greater delay in elongation of the apical buds than species with low resistance Sprout more freely from basal buds after defoliation than species with low resistance. Higher ratio of vegetative to reproductive stems than species with low resistance.

136 Return to Course Map Grazing and Plant Growth Forbs Produce a large number of viable seeds Delayed elevation of growing points Poisons and chemical compounds that reduce palatability

137 Return to Course Map Grazing and Plant Growth Shrubs Spines and thorns volatile oils and tannins that reduce palatability Branches make removal of inner leaves difficult Only current years growth is palatable and nutritious for most species.

138 Return to Course Map Grazing and Plant Growth Most to least resistant 1. Grasses 2. Shrubs 3. Forbs *Many exceptions do occur.

139 Return to Course Map Grazing and Plant Growth In the final section you learned about grazing and plant responses to grazing. You learned that grazing can have detrimental as well as growth promoting effects on plants. We discussed the theory of grazing optimization and some of the mechanisms that can result in compensatory plant growth. And finally we discussed mechanisms that allow plants to resist the effects of grazing.

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141 The Phenology Handbook, pg 1-15 George et al Annual Range Forage Production George and Bell Using Stage of Maturity…….. Return to Course Map Seasonality and Seasonality and Life Cycles Life Cycles SEASONALITY & LIFE CYCLES

142 Briske, Chp 4. Dev. Morph and Phys of Grasses. Introduction and Developmental Morphology Sections. Skinner and Moore. Growth and Dev of Forage Plants How Grass Grows MORPHOLOGY

143 McKell, C.M Morphogenesis and management of annual range plants in the United States. Pg Briske, Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section. Waller and Lewis Occurrence of C3 and C4 photosynthetic pathways in North American grasses. Carbohydrate Reserves: What you learned may be wrong.

144 Briske, Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section. Trlica, J Grass Growth and Response to Grazing. A quick lesson in plant structure, growth and regrowth for pasture-based dairy systems. Noy-Meir, I Compensating growth of grazed plants and its relevance to the use of rangelands.

145 McKell, C.M Morphogenesis and management of annual range plants in the United States. Pg Briske, Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section. Waller and Lewis Occurrence of C3 and C4 photosynthetic pathways in North American grasses. Carbohydrate Reserves: What you learned may be wrong.

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147 Grass Anatomy Growing Points (buds, meristems) Developmental Anatomy Forb Anatomy Growing Points (buds, meristems) Reproduction Sexual Asexual Return to Course Map Morphology

148 Germination and Seedling Establishment Germination and Seedling Establishment Photosynthesis Factors that influence photosysnthesis C3, C4, CAM Photosynthesis Carbohydrates and Carbohydrate Allocation Water and Nutrients Secondary Compounds Plant Physiology Return to Course Map

149 Grazing and Plant Growth Grazing Effects Grazing Optimization Grazing Resistance Return to Course Map

150 Plant Physiology Morphology Seasonality and Life Cycle Grazing and Plant Growth Life Cycles And Phenology Seasonal Growth Rates Germination and seeding establishment Grazing Optimization Carbohydrates and Carb. Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients

151 Plant Physiology Morphology Seasonality and Life Cycle Grazing and Plant Growth Life Cycles And Phenology Seasonal Growth Rates Germination and seeding establishment Grazing Optimization Carbohydrates and Carb. Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients

152 Plant Physiology Morphology Seasonality and Life Cycle Grazing and Plant Growth Life Cycles And Phenology Seasonal Growth Rates Germination and seeding establishment Grazing Optimization Carbohydrates and Carb. Allocation Reproduction Grass Anatomy Forb Anatomy Shrub Anatomy You are here Secondary Compounds Grazing Resistance Forage Quality RDM Grazing Effects Photosynthesis Water and Nutrients

153 1. Basic concepts of plant growth 2. Importance of carbohydrate reserves 3. Grazing effect on forage plants 4. Grazing resistance in grasses, forbs and shrubs 5. Grazing theory a. Why palatable plants dominate rangelands with good grazing management? b. Why unpalatable plants dominate rangelands under sustained heavy grazing (over grazing)?

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155 1. Plants must have leaves for photosynthesis. 2. Grazing has the least effect on plants during the dormant season when they are photosynthetically inactive. 3. Grazing has the most severe effect on plants towards the end of the growing season ( seed formation to seed hardening) because the plants demands for carbohydrates are higher and little time remains of optimal temperature and moisture conditions for regrowth. 4. Grazing early in the growing season has less effect on plants than late in the growing season because considerable time remains when temperature and moisture are optimal for regrowth.

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157 1. Root replacement and growth 2. Regeneration of leaves and stems after dormancy 3. Respiration during dormancy 4. Bud formation 5. Regrowth after top removal by grazing.

158 Factors that influence photosysnthesis C3, C4, CAM Photosynthesis Carbohydrates and Carbohydrate Allocation

159 Recruitment maintains plant community Sexual Reproduction (flowers and seeds) Vegetative Reproduction (stolons, rhizomes) Annuals dependent on seed production Short-lived perennials depend on seed production Long-lived perennials rely more on vegetative reproduction.

160 Relationship between herbage dry matter and leaf area (Brougham 1956)

161 Increased photosynthesis

162 Increased tillering Increased photosynthesis Reduced transpiration

163 Reduced shading

164 Reduced transpiration

165 Increased plant productivity Increased tillering Reduced shading of lower leaves Reduced transpiration losses Reduced ability to compete with ungrazed plants Reduction of excessive litter or mulch that can physically or chemically inhibit vegetative growth. Excessive mulch promotes pathogens and insects that can damage forage plants.

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174 Return to Course Map

175 Bilbrough and Richards (1993) C = control no clipping TB = terminal bud removed only 60 = 60% current annual growth removed 100 = 100% current annual growth removed Return to Course Map Grazing and Plant Growth

176 Return to Course Map Grazing and Plant Growth

177 1. Root replacement and growth 2. Regeneration of leaves and stems after dormancy 3. Respiration during dormancy 4. Bud formation 5. Regrowth after top removal by grazing. Return to Course Map Grazing and Plant Growth We can probably delete this slide

178 GRAZING OPTIMIZATION Return to Course Map Grazing and Plant Growth Can probably delete this slide


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