While plants do produce various secondary metabolites, gum arabic is a complex polysaccharide exudate used by the plant for wound sealing and protection, rather than a metabolic waste product like oxygen, CO2, or water vapor.

The 'Coorg' and 'Kents' varieties are widely recognized cultivars of Coffea arabica (Coffee). These varieties were developed for their specific traits, such as yield, disease resistance, and flavor profiles. They are significant in the agricultural industry, particularly in regions like India where Coorg is a major coffee-growing area. Note: The source text contains a typo 'CofJea', which is corrected here to Coffea.

Acacia nilotica, formerly known as Acacia arabica, is the national tree of Pakistan. It is a drought-resistant, nitrogen-fixing tree that is widely distributed across the country. It provides valuable timber, fodder, and fuel, and is highly valued for its ecological role in stabilizing soil and providing shade in arid landscapes.

Coffea arabica is a tetraploid species, meaning it possesses four sets of chromosomes (44 in total) rather than the two sets found in diploid coffee species. This polyploidy is a defining characteristic of Arabica coffee, which accounts for approximately 60% of global coffee production. Its unique genetic makeup contributes to its specific flavor profile and cultivation requirements compared to other coffee species.

Unlike Arabica coffee, which is largely self-pollinating, Robusta coffee (Coffea canephora) is an obligate cross-pollinator. It requires external agents such as wind and insects, particularly bees, to transfer pollen between genetically distinct individuals to achieve successful fertilization. This cross-pollination behavior is essential for fruit set and contributes to the genetic diversity found within Robusta populations.

Acacia nilotica, commonly known as Acacia arabica or the Kikar tree, is designated as the national tree of Pakistan. It is highly valued for its adaptability to arid and semi-arid climates, its role in soil conservation, and its utility in providing timber, fodder, and medicinal products in various regions of the country.

Rabi crops are agricultural crops sown in winter and harvested in the spring in the Indian subcontinent. The term 'Rabi' is derived from the Arabic word for 'spring'. These crops require a cool climate during the growth period and a warm climate during the maturation phase, typically spanning from October to March.

Dhurrin is a cyanogenic glycoside found in sorghum plants. Under stress conditions, such as drought or high temperatures, the plant can accumulate this compound. When consumed by livestock, dhurrin is hydrolyzed to release hydrogen cyanide, which is highly toxic and can lead to fatal poisoning. The name 'dhurrin' is derived from the Arabic term for sorghum, highlighting the historical recognition of this plant's potential toxicity to grazing animals.

Stickers are additives used in pesticide formulations to improve the adhesion of the spray solution to the plant surface, preventing runoff and wash-off. Fish oil, linseed oil, and gum arabic are all recognized as effective stickers. By increasing the tenacity of the chemical deposit on foliage, these substances ensure that the pesticide remains effective for a longer duration, even under adverse weather conditions like rain or high humidity.

Step-by-step solution: 1. Use Zeller's congruence to compute the day of the week. 2. After substituting the values, remainder corresponds to Friday. 3. Therefore, 25/8/2023 fell on a Friday.