Abiotic Disorders in Plants Lecture Notes PDF

ABIOTIC DISORDERS IN PLANTS CPRT 41 Lecture Material on First Semester SY 2023-2024 Prepared by : Dr. Carolina D. Amper Faculty, Department of Plant Pathology ABIOTIC DISORDERS Plants can be damaged by noninfectious factors, causing problems that can collectively be termed...

ABIOTIC DISORDERS IN PLANTS CPRT 41 Lecture Material on First Semester SY 2023-2024 Prepared by : Dr. Carolina D. Amper Faculty, Department of Plant Pathology ABIOTIC DISORDERS Plants can be damaged by noninfectious factors, causing problems that can collectively be termed "abiotic diseases" or "abiotic disorders". Unfavorable soil properties, fertility imbalances, moisture extremes, temperature extremes, chemical toxicity, physical injuries, and other problems are examples of abiotic disorders that can reduce plant health and even kill plants. Furthermore, many of these abiotic disorders can predispose plants to diseases caused by infectious microbes. SOIL STRUCTURE Soil structure determines the soil's ability to hold water, nutrients, and oxygen and make them available to plants. The most common issue related to soil structure is compaction, which results in inadequate pore space for root growth. SOIL pH Soil pH is the measure of the H + ion activity in the soil solution. A high amount of H + activity results in an acidic soil condition, while low activity results in a predominance of OH - activity, leading to alkaline soil. Although some plant species have preferences for more extreme acidic or alkaline soil conditions, it is generally regarded that a slightly acidic pH range of 6-7 is most favorable for plant growth. Symptoms due to low pH NUTRIENT TOXICITIES Damage from excessive macronutrient levels can occur in crop and ornamental plants as the result of over-application of fertilizers or manures Micronutrient toxicities are common in many production systems. Symptoms often include chlorosis or necrosis on leaf margins or tips, but leaf spotting, flecking, and other symptoms can occur. NUTRIENT DEFICIENCIES Nutrient deficiencies often result from a lack of plant nutrients in the soil Nitrogen (N) deficiency is a major limitation for non- leguminous agricultural plants. Plants deficient in N typically have a pale yellow color (chlorosis) as a result of reduced chlorophyll production Plants that are deficient in N may also appear stunted and display poor vigor. Plants deficient in P have weaker stems, which can result in problems such as lodging in grain crops. Phosphorus deficiency can also result in poor growth and stunting, a blue/green hue to the leaves, and/or purple-colorations to stems and undersides of the leaves. NUTRIENT DEFICIENCIES (cont.) Plants with an Fe deficiency typically have similar leaf size/shape compared to normal plants, but will display interveinal chlorosis. Symptoms first develop in the new growth which appears as yellow-green leaves, often with a striped appearance. Blossom end rot is a common symptom of Ca deficiency on fruits. Other symptoms manifest as plant stunting, localized tissue necrosis, and leaf marginal chlorosis Nutrient Deficiencies Nitrogen deficiency Phosphorus deficiency Nutrient Deficiencies Iron deficiency Calcium deficiency  MOISTURE EXTREMES Low water status in plants can occur either as a short-term or chronic deficiency. A short-term deficit of water might result in only minor effects on the plant such as wilted leaves or shoots Excessive soil moisture can result in reduced oxygen availability to roots. Therefore, similar to drought, a primary symptom of flooding is plant wilt. Also similar to low water status, excess soil moisture can manifest as acute or chronic. TEMPERATURE EXTREMES If high temperatures are coupled with low soil moisture, plants may exhibit scorching on the margins of the leaves, premature leaf drop, and in severe cases entire plant death. Damage from low temperatures generally develops because ice crystals form in plant cells resulting in damage to cell membranes and organelles. CHEMICAL INJURIES/TOXICITIES Some herbicides cause root stunting or swelling, and could be confused with damage from nematodes. Others herbicides cause necrotic/chlorotic spots or blotches that could be confused with a foliar disease. Some herbicides cause mottled colors, distortion or vein banding that could be confused with a viral disease. AIR POLLUTION AND DAMAGING GASES Several gaseous air pollutants can cause injury to plants, including ozone and sulfur dioxide. Ozone can cause flecking), which could be mistaken for mite injury. Ozone can also cause bronzing, chlorosis, and necrosis. Necrosis could be mistaken for a leaf spot caused by an infectious agent. In conifers, injury can include needle-banding and tip-burn. STORM DAMAGE Storms that produce high winds, heavy snow or ice loads can result in significant limb breakage. High winds can knock down trees that have been predisposed to damage by root and butt rots or wood decay in the lower portion of the tree. Some trees are killed outright. END