Decreased Photosynthetic Efficiency in Nicotiana tabacum L. under Transient Heat Stress.

Heat stress is an abiotic factor that affects the photosynthetic parameters of plants. In this study, we examined the photosynthetic mechanisms underlying the rapid response of tobacco plants to heat stress in a controlled environment. To evaluate transient heat stress conditions, changes in photochemical, carboxylative, and fluorescence efficiencies were measured using an infrared gas analyser (IRGA Licor 6800) coupled with chlorophyll a fluorescence measurements. Our findings indicated that significant disruptions in the photosynthetic machinery occurred at 45 °C for 6 h following transient heat treatment, as explained by 76.2% in the principal component analysis. The photosynthetic mechanism analysis revealed that the dark respiration rate (Rd and Rd*CO2) increased, indicating a reduced potential for carbon fixation during plant growth and development. When the light compensation point (LCP) increased as the light saturation point (LSP) decreased, this indicated potential damage to the photosystem membrane of the thylakoids. Other photosynthetic parameters, such as AMAX, VCMAX, JMAX, and ΦCO2, also decreased, compromising both photochemical and carboxylative efficiencies in the Calvin-Benson cycle. The energy dissipation mechanism, as indicated by the NPQ, qN, and thermal values, suggested that a photoprotective strategy may have been employed. However, the observed transitory damage was a result of disruption of the electron transport rate (ETR) between the PSII and PSI photosystems, which was initially caused by high temperatures. Our study highlights the impact of rapid temperature changes on plant physiology and the potential acclimatisation mechanisms under rapid heat stress. Future research should focus on exploring the adaptive mechanisms involved in distinguishing mutants to improve crop resilience against environmental stressors.

Cotton productivity enhanced through transplanting and early sowing / Aumento da produtividade do algodão por meio de transplante de mudas e semeadura precoce

Due to high temperatures in arid regions, cotton crop emergence and early establishment ofseedlings are adversely affected. Field studies were undertaken to quantify the effects of transplantation ofcotton (Gossypium hirsutum L.) seedlings during the early part of the growing season (March) and cropseason (May) for potential realization of cotton productivity under the harsh weather of the southern partof Punjab province, Pakistan. Treatments, consisting of (a) two planting dates (March and May), and (b)two sowing methods (transplanting of seedlings and direct seeding), were arranged in a randomizedcomplete-block design with four replications. Results showed that transplanting seedlings improved theproductivity of cotton by 14.2% over direct seeding. Productivity was also increased substantially (34.8%)by planting during March over May sowing. The practice of planting cotton by transplanting seedlings andearly sowing could be successfully adapted in areas where high temperatures coincide with the Mayplanting and peak blooming periods in different cotton growing areas.

Altas temperaturas, em torno de 48ºC, prevalecem durante os meses de maio na parte do sul da província de Punjab, no Paquistão. A esta temperatura a emergência da colheita de algodão e o estabelecimento precoce da plântula são adversamente afetados. Estudos de campo foram realizados paraquantificar os efeitos do transplante de mudas de algodão (Gossypium hirsutum L.) durante a primeira parteda estação de crescimento (março) e da safra (maio) para a realização potencial da produtividade do algodãosob condições adversas da parte sul do Punjab Província-Paquistão. Os tratamentos, consistindo em(a) duas datas de plantio (março e maio), e (b) dois métodos de semeadura (transplante de mudas e semeadura direta), foram dispostos em delineamento em blocos ao acaso com quatro repetições. Os resultados mostraram que o transplante de mudas melhorou a produtividade do algodão em 14,2% em relação à semeadura direta. A produtividade também aumentou substancialmente (34,8%) com o plantioem março sobre a semeadura de maio. A prática de plantio de algodão por transplante de mudas e sua semeadura precoce poderia ser adaptada com sucesso, onde a alta temperatura coincide com o tempo de plantio durante o mês de maio e períodos de florescimento máximo em diferentes áreas de cultivo de algodão.

Cotton productivity enhanced through transplanting and early sowing

Due to high temperatures in arid regions, cotton crop emergence and early establishment of seedlings are adversely affected. Field studies were undertaken to quantify the effects of transplantation of cotton (Gossypium hirsutum L.) seedlings during the early part of the growing season (March) and crop season (May) for potential realization of cotton productivity under the harsh weather of the southern part of Punjab province, Pakistan. Treatments, consisting of (a) two planting dates (March and May), and (b) two sowing methods (transplanting of seedlings and direct seeding), were arranged in a randomized complete-block design with four replications. Results showed that transplanting seedlings improved the productivity of cotton by 14.2% over direct seeding. Productivity was also increased substantially (34.8%) by planting during March over May sowing. The practice of planting cotton by transplanting seedlings and early sowing could be successfully adapted in areas where high temperatures coincide with the May planting and peak blooming periods in different cotton growing areas.

Cotton productivity enhanced through transplanting and early sowing

Due to high temperatures in arid regions, cotton crop emergence and early establishment of seedlings are adversely affected. Field studies were undertaken to quantify the effects of transplantation of cotton (Gossypium hirsutum L.) seedlings during the early part of the growing season (March) and crop season (May) for potential realization of cotton productivity under the harsh weather of the southern part of Punjab province, Pakistan. Treatments, consisting of (a) two planting dates (March and May), and (b) two sowing methods (transplanting of seedlings and direct seeding), were arranged in a randomized complete-block design with four replications. Results showed that transplanting seedlings improved the productivity of cotton by 14.2% over direct seeding. Productivity was also increased substantially (34.8%) by planting during March over May sowing. The practice of planting cotton by transplanting seedlings and early sowing could be successfully adapted in areas where high temperatures coincide with the May planting and peak blooming periods in different cotton growing areas.

Cotton productivity enhanced through transplanting and early sowing / Aumento da produtividade do algodão por meio de transplante de mudas e semeadura precoce

Due to high temperatures in arid regions, cotton crop emergence and early establishment ofseedlings are adversely affected. Field studies were undertaken to quantify the effects of transplantation ofcotton (Gossypium hirsutum L.) seedlings during the early part of the growing season (March) and cropseason (May) for potential realization of cotton productivity under the harsh weather of the southern partof Punjab province, Pakistan. Treatments, consisting of (a) two planting dates (March and May), and (b)two sowing methods (transplanting of seedlings and direct seeding), were arranged in a randomizedcomplete-block design with four replications. Results showed that transplanting seedlings improved theproductivity of cotton by 14.2% over direct seeding. Productivity was also increased substantially (34.8%)by planting during March over May sowing. The practice of planting cotton by transplanting seedlings andearly sowing could be successfully adapted in areas where high temperatures coincide with the Mayplanting and peak blooming periods in different cotton growing areas.(AU)

Altas temperaturas, em torno de 48ºC, prevalecem durante os meses de maio na parte do sul da província de Punjab, no Paquistão. A esta temperatura a emergência da colheita de algodão e o estabelecimento precoce da plântula são adversamente afetados. Estudos de campo foram realizados paraquantificar os efeitos do transplante de mudas de algodão (Gossypium hirsutum L.) durante a primeira parteda estação de crescimento (março) e da safra (maio) para a realização potencial da produtividade do algodãosob condições adversas da parte sul do Punjab Província-Paquistão. Os tratamentos, consistindo em(a) duas datas de plantio (março e maio), e (b) dois métodos de semeadura (transplante de mudas e semeadura direta), foram dispostos em delineamento em blocos ao acaso com quatro repetições. Os resultados mostraram que o transplante de mudas melhorou a produtividade do algodão em 14,2% em relação à semeadura direta. A produtividade também aumentou substancialmente (34,8%) com o plantioem março sobre a semeadura de maio. A prática de plantio de algodão por transplante de mudas e sua semeadura precoce poderia ser adaptada com sucesso, onde a alta temperatura coincide com o tempo de plantio durante o mês de maio e períodos de florescimento máximo em diferentes áreas de cultivo de algodão.(AU)