Biochemical responses in leaf tissues of alkaloid producing Psychotria brachyceras under multiple stresses.

Under natural conditions plants are generally subjected to complex scenarios of combined or sequential environmental stresses. Among the various components of plant biochemistry modulated by abiotic variables, a pivotal role is played by antioxidant systems, including specialized metabolites and their interaction with central pathways. To help address this knowledge gap, a comparative analysis of metabolic changes in leaf tissues of the alkaloid accumulating plant Psychotria brachyceras Müll Arg. under individual, sequential, and combined stress conditions was carried out. Osmotic and heat stresses were evaluated. Protective systems (accumulation of the major antioxidant alkaloid brachycerine, proline, carotenoids, total soluble protein, and activity of the enzymes ascorbate peroxidase and superoxide dismutase) were measured in conjunction with stress indicators (total chlorophyll, ChA/ChB ratio, lipid peroxidation, H2O2 content and electrolyte leakage). Metabolic responses had a complex profile in sequential and combined stresses compared to single ones, being also modified over time. Different stress application schemes affected alkaloid accumulation in distinct ways, exhibiting similar profile to proline and carotenoids, constituting a complementary triad of antioxidants. These complementary non-enzymatic antioxidant systems appeared to be essential for mitigating stress damage and re-establishing cellular homeostasis. The data herein provides clues that may aid the development of a key component framework of stress responses and their appropriate balance to modulate tolerance and yield of target specialized metabolites.

Developmental plasticity in Arabidopsis thaliana under combined cold and water deficit stresses during flowering stage.

MAIN CONCLUSION: Morpho-physiological changes were observed in Arabidopsis plants acclimated to long-term combined cold and water deficit stresses. Limiting growth and differences in bolting, flowering, and silique development were evidenced. In nature, plants are exposed to multiple and simultaneous abiotic stresses that influence their growth, development, and reproduction. In the last years, the study of combined stresses has aroused the interest to know the physiological and molecular responses, because these new stress conditions are probed to be different from the sum of the individual stress. We are interested in the study of the acclimation of plants growing under the combination of cold and water deficit stresses prevalent in cold-arid or semi-arid climates worldwide. We hypothesized that the reproduction of the acclimated plants will be compromised and affected. Arabidopsis plants were submitted to long-term combined stress from the beginning to the reproductive stage, when floral bud was visible, until the silique development. Our results demonstrate severe morpho-anatomical changes after acclimation to combined stress. Inflorescence stem morphology was altered having a delayed bolting and a limited growth. Flowering and silique formation were delayed, and a higher size in the corolla and the petals was observed. Flower and silique number were severely diminished as a result of combined stress, unlike acclimated plants to individual cold stress. These traits were recovered after deacclimation to optimal conditions and plants achieved similar silique production as control plants. The long-term stress results suggest that there is not a single dominant stress, but there is an alternating dominance depending on the structure or the plant stage development evaluated.

Impact of heat stress, nutritional stress and their combinations on the adaptive capability of Malpura sheep under hot semi-arid tropical environment

A study was conducted to assess the cumulative effects of combined stresses (heat and nutritional) on physiological adaptability, blood biochemical and endocrine responses in Malpura rams. The study was conducted for a period of 45 days. Twenty eight adult Malpura rams (average BW 66.0 Kg) were used in the present study. The rams were divided into four groups viz., CON (n=7; control), HS (n=7; heat stress), NS (n=7; nutritional stress) and CS (n=7; combined stress). The animals were stall fed with a diet consisting of 60% roughage and 40% concentrate. The CON and HS ewes were provided with ad libitum feeding while NS and CS rams were provided with restricted feed (30% intake of GI ewes) to induce nutritional stress. The HS and NS rams were kept in climatic chamber @ 42ºC and 55% RH for six hours a day between 10:00 hr to 16:00 hr to induce heat stress. The parameters studied were respiration rate (RR), pulse rate (PR), rectal temperature (RT), scrotal volume, sweating rate scrotum, sweating rate skin, haemoglobin (Hb) and packed cell volume (PCV), plasma cortisol, T3 (tri-iodo-thyronine), and T4 (thyroxin) level. Combined stresses significantly (P<0.01) influenced all adaptive parameters studied. The study shows that Malpura rams possess the adaptive capability to two stresses simultaneously. This is evident from the non-significant changes in RR, RT, sweating rate of scrotum and skin and Hb concentration between HS and CS groups. Further, the capability to adjust the cortisol level to minimum possible increase to elicit the heat stress relieving effects also proves the superior adaptive capability of Malpura rams to the effects of combined stresses.

Impact of heat stress, nutritional stress and their combinations on the adaptive capability of Malpura sheep under hot semi-arid tropical environment

A study was conducted to assess the cumulative effects of combined stresses (heat and nutritional) on physiological adaptability, blood biochemical and endocrine responses in Malpura rams. The study was conducted for a period of 45 days. Twenty eight adult Malpura rams (average BW 66.0 Kg) were used in the present study. The rams were divided into four groups viz., CON (n=7; control), HS (n=7; heat stress), NS (n=7; nutritional stress) and CS (n=7; combined stress). The animals were stall fed with a diet consisting of 60% roughage and 40% concentrate. The CON and HS ewes were provided with ad libitum feeding while NS and CS rams were provided with restricted feed (30% intake of GI ewes) to induce nutritional stress. The HS and NS rams were kept in climatic chamber @ 42ºC and 55% RH for six hours a day between 10:00 hr to 16:00 hr to induce heat stress. The parameters studied were respiration rate (RR), pulse rate (PR), rectal temperature (RT), scrotal volume, sweating rate scrotum, sweating rate skin, haemoglobin (Hb) and packed cell volume (PCV), plasma cortisol, T3 (tri-iodo-thyronine), and T4 (thyroxin) level. Combined stresses significantly (P<0.01) influenced all adaptive parameters studied. The study shows that Malpura rams possess the adaptive capability to two stresses simultaneously. This is evident from the non-significant changes in RR, RT, sweating rate of scrotum and skin and Hb concentration between HS and CS groups. Further, the capability to adjust the cortisol level to minimum possible increase to elicit the heat stress relieving effects also proves the superior adaptive capability of Malpura rams to the effects of combined stresses.(AU)

Impact of heat stress, nutritional stress and combined (heat and nutritional) stresses on rumen associated fermentation characteristics, histopathology and HSP70 gene expression in goats

A study was conducted to assess the impact of heat stress, nutritional stress and combined stresses (heat and nutritional stress) on rumen fermentation characteristics, histopathology of rumen and rumen HSP70 gene expression in goats. Twenty four adult Osmanabadi bucks were divided into four groups, C (n=6; control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined stress). The study was conducted for a period of 45 days. The C and HS bucks had ad libitum access to their feed while NS and CS bucks were subjected to restricted feed (30% intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to heat stress in an outside environment. Both feed intake and body weight were significantly (p < 0.01) lower in CS and NS groups. The carboxy methyl cellulase activities - extracellular, intracellular and total activity in the rumen fluid differed significantly (p < 0.01) between the groups. The highest concentration of ammonia nitrogen (p < 0.05) was recorded in C while the lowest in the CS group. The concentration of total nitrogen and trichloroacetic acid precipitable N, propionic acid, butyric acid, and valeric acid was lower (p < 0.01) in the restricted fed (NS and CS) bucks as compared to ad libitum fed groups (C and HS). Further, the ratio of acetate to propionate (A: P ratio) was also significantly (p < 0.01) higher in CS and NS groups. The higher expression of rumen heat shock protein 70 (HSP70) mRNA was observed in CS goats. The histopathological section of rumen revealed a reduction in the length of rumen villi and thickness in CS, whereas rumen keratinization was highest in the CS group. From the study it can be concluded that when two stresses occur simultaneously, they may have severe impact on rumen fermentation characteristics of bucks.

Impact of heat stress, nutritional stress and combined (heat and nutritional) stresses on rumen associated fermentation characteristics, histopathology and HSP70 gene expression in goats

A study was conducted to assess the impact of heat stress, nutritional stress and combined stresses (heat and nutritional stress) on rumen fermentation characteristics, histopathology of rumen and rumen HSP70 gene expression in goats. Twenty four adult Osmanabadi bucks were divided into four groups, C (n=6; control), HS (n=6; heat stress), NS (n=6; nutritional stress) and CS (n=6; combined stress). The study was conducted for a period of 45 days. The C and HS bucks had ad libitum access to their feed while NS and CS bucks were subjected to restricted feed (30% intake of C bucks) to induce nutritional stress. The HS and CS bucks were exposed to heat stress in an outside environment. Both feed intake and body weight were significantly (p < 0.01) lower in CS and NS groups. The carboxy methyl cellulase activities - extracellular, intracellular and total activity in the rumen fluid differed significantly (p < 0.01) between the groups. The highest concentration of ammonia nitrogen (p < 0.05) was recorded in C while the lowest in the CS group. The concentration of total nitrogen and trichloroacetic acid precipitable N, propionic acid, butyric acid, and valeric acid was lower (p < 0.01) in the restricted fed (NS and CS) bucks as compared to ad libitum fed groups (C and HS). Further, the ratio of acetate to propionate (A: P ratio) was also significantly (p < 0.01) higher in CS and NS groups. The higher expression of rumen heat shock protein 70 (HSP70) mRNA was observed in CS goats. The histopathological section of rumen revealed a reduction in the length of rumen villi and thickness in CS, whereas rumen keratinization was highest in the CS group. From the study it can be concluded that when two stresses occur simultaneously, they may have severe impact on rumen fermentation characteristics of bucks.(AU)