Write short notes on the following in about 150 words each: (a) Symptoms of mineral deficiencies (10 marks) (b) RAPD PCR –…

Symptoms of Mineral Deficiencies Mineral deficiency symptoms in plants are diagnostic indicators of nutrient imbalance, varying based on the mobility of the element within the phloem. Nitrogen, being mobile, shows symptoms in older leaves first, manifesting as general chlorosis (yellowing) and stunted growth due to reduced protein synthesis. Phosphorus deficiency results in dark green or purplish leaves, poor root development, and delayed maturity, often accompanied by necrotic spots. Potassium deficiency, also mobile, causes marginal leaf scorching (necrosis) and weak stems leading to lodging, as it regulates stomatal function and structural integrity. In contrast, immobile micronutrients like Iron and Manganese show symptoms in young, expanding leaves. Iron deficiency causes interveinal chlorosis where veins remain green while the interveinal tissue yellows. Manganese deficiency in oats is known as "grey speck," characterized by greyish-brown spots on young leaves. Distinguishing between mobile and immobile nutrients is critical for accurate diagnosis and targeted fertilization strategies in agricultural management.

RAPD PCR Random Amplified Polymorphic DNA (RAPD) PCR is a molecular marker technique using a single, arbitrary 10-base oligonucleotide primer to amplify random segments of genomic DNA. Its primary strength lies in its simplicity; it requires no prior knowledge of the target sequence, making it rapid, cost-effective, and highly versatile for initial genetic screening. It is widely applied in assessing genetic diversity, cultivar identification, and constructing phylogenetic trees in plant breeding programs. However, RAPD has significant weaknesses. The markers are dominant, meaning heterozygotes cannot be distinguished from homozygotes, limiting the precision of genetic mapping. Reproducibility is often low due to sensitivity to minor variations in PCR conditions, such as annealing temperature and primer concentration. Furthermore, the technique is highly susceptible to contamination, as even trace amounts of foreign DNA can produce spurious bands. Despite these limitations, RAPD remains a valuable tool for preliminary studies where high-resolution genotyping is not yet required.

Photophosphorylation Photophosphorylation is the light-dependent process of ATP synthesis in chloroplasts, driven by the energy of photons. It occurs in two modes: non-cyclic and cyclic. In non-cyclic photophosphorylation, both Photosystem II (PS-II) and Photosystem I (PS-I) are involved. Light excites electrons in PS-II, which are passed through an electron transport chain to PS-I, generating a proton gradient across the thylakoid membrane. This gradient drives ATP synthase (CF0-CF1 complex) to produce ATP via chemiosmosis. Cyclic photophosphorylation involves only PS-I, where electrons cycle back to the reaction center, producing ATP without NADPH or oxygen evolution. This process helps balance the ATP/NADPH ratio required for the Calvin cycle. According to the chemiosmotic theory, the flow of protons down their electrochemical gradient through ATP synthase is the direct mechanism of energy conversion, with approximately three protons required for the synthesis of one ATP molecule.

Endangered Plant Species Endangered plant species are those facing a very high risk of extinction in the wild, as defined by the IUCN Red List. The IUCN categorizes species into Critically Endangered (CR), Endangered (EN), and Vulnerable (VU), collectively termed "threatened." Listing criteria (A-E) assess population decline, geographic range, and population size. In India, notable examples include Pterocarpus santalinus (Red Sanders), listed as Endangered due to illegal logging for its valuable red heartwood; Nepenthes khasiana, a pitcher plant endemic to Meghalaya, threatened by habitat loss; and Saussurea obvallata (Brahma Kamal), a high-altitude medicinal plant in the Himalayas, vulnerable to climate change and over-harvesting. The primary drivers of endangerment include habitat destruction from deforestation and urbanization, overexploitation for medicinal and ornamental purposes, and the spread of invasive alien species. Conservation efforts involve ex-situ cultivation in botanical gardens and in-situ protection within national parks, guided by the Wildlife Protection Act and CITES regulations.

Phytoremediation Phytoremediation is an eco-friendly technology using plants to remove, degrade, or immobilize pollutants from soil, water, and air. Key mechanisms include phytoextraction, where plants absorb and accumulate heavy metals in their shoots for harvest; phytostabilization, which reduces pollutant mobility by binding them in the root zone; phytodegradation, where plants or associated microbes break down organic contaminants; phytovolatilization, where plants convert pollutants into volatile forms released into the atmosphere; and rhizofiltration, which cleans water by absorbing pollutants through roots. Hyperaccumulator species are particularly effective; for instance, Brassica juncea (Mustard) accumulates selenium, Helianthus annuus (Sunflower) extracts lead, and Vetiveria zizanioides stabilizes eroded soils. Advantages include low cost, minimal soil disturbance, and aesthetic appeal. Limitations include slow remediation rates, limited depth of root penetration, and the need for proper disposal of harvested biomass to prevent secondary contamination.