Interação entre o déficit hídrico e a disponibilidade de nitrogênio nas trocas gasosas e no metabolismo secundário de Amaranthus cruentus L.
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Data
2021-08-20
Autores
Silva, Laura Prado da
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Universidade Estadual Paulista (Unesp)
Resumo
A disponibilidade de água e nitrogênio são fatores ambientais que podem prejudicar o crescimento das plantas e, quando combinados, seus efeitos podem ser intensificados ou reduzidos. O objetivo deste estudo foi analisar a influência da disponibilidade de nitrogênio nas respostas metabólicas de Amaranthus cruentus L. ao estresse hídrico. As plantas foram cultivadas em vasos plásticos tendo como substrato a vermiculita, e foram mantidas na casa de vegetação sendo irrigadas com a solução de Long Ashton a 70% contendo 1,97 ou 9,88 kg N ha –1 de nitrato de amônio, três vezes por semana. As plantas foram estressadas por suspensão da rega após 42 dias de crescimento. Foram avaliados os parâmetros fotossintéticos das plantas e as folhas foram colhidas para análise química. O maior suprimento de nitrogênio aumentou a matéria seca da parte aérea, os pigmentos fotossintéticos, a fotossíntese, a condutância estomática, a transpiração, o nitrogênio foliar total, a prolina, o nitrato e o amônio, mas reduziu a concentração de flavonoides e fenóis totais. O estresse hídrico por seis dias não afetou a matéria seca, os pigmentos fotossintéticos, o nitrogênio foliar, o amônio e os metabólitos especializados, mas aumentou a prolina e afetou negativamente as demais variáveis. As interações observadas entre o nitrogênio e o suprimento de água resultaram em nenhum alívio dos efeitos negativos da seca sobre o amaranto. Embora o aumento da disponibilidade de nitrogênio tenha beneficiado o desempenho das plantas, intensificou o efeito negativo do estresse hídrico. Após 24 horas de reidratação, as plantas foram capazes de se recuperar do efeito negativo do estresse hídrico.
Water and nitrogen availability are environmental factors that can impair plant growth, andwhen they are combined their effects can be intensified or reduced. The objective of this study was to analyse the influence of nitrogen availability on the responses of Amaranthus cruentus's metabolisms to water stress. The plants were cultivated in plastic pots lled with vermiculite and kept under greenhouse conditions and were watered with 70% of full strength nitrogen-free Long Ashton solution, containing 1.97 or 9.88 kg N ha -1 as ammonium nitrate, three times a week. The plants were stressed by suspension of watering after after 42 days of growth. Photosynthetic parameter were evaluated in planta and leaves were harvested for chemical analysis. Higher nitrogen supply increased the shoot dry matter, photosynthetic pigments, photosynthesis, stomatal conductance, transpiration, total leaf nitrogen, proline, nitrate and ammonium but reduced the concentration of flavonoids and total phenols. Water stress for 6 days did not affect dry matter, photosynthetic pigments, leaf nitrogen, ammonium or specialized metabolites but increased the proline and affected negatively the other variables. The observed interactions between nitrogen and water supply resulted in no alleviation of the negative effects of drought on amaranth. Although the increase in nitrogen supply had benefits on plant performance, it intensifield the negative effect of water stress. After 24 h of rehydration, the plants were able to recovery from the negative effect of water stress.
Water and nitrogen availability are environmental factors that can impair plant growth, andwhen they are combined their effects can be intensified or reduced. The objective of this study was to analyse the influence of nitrogen availability on the responses of Amaranthus cruentus's metabolisms to water stress. The plants were cultivated in plastic pots lled with vermiculite and kept under greenhouse conditions and were watered with 70% of full strength nitrogen-free Long Ashton solution, containing 1.97 or 9.88 kg N ha -1 as ammonium nitrate, three times a week. The plants were stressed by suspension of watering after after 42 days of growth. Photosynthetic parameter were evaluated in planta and leaves were harvested for chemical analysis. Higher nitrogen supply increased the shoot dry matter, photosynthetic pigments, photosynthesis, stomatal conductance, transpiration, total leaf nitrogen, proline, nitrate and ammonium but reduced the concentration of flavonoids and total phenols. Water stress for 6 days did not affect dry matter, photosynthetic pigments, leaf nitrogen, ammonium or specialized metabolites but increased the proline and affected negatively the other variables. The observed interactions between nitrogen and water supply resulted in no alleviation of the negative effects of drought on amaranth. Although the increase in nitrogen supply had benefits on plant performance, it intensifield the negative effect of water stress. After 24 h of rehydration, the plants were able to recovery from the negative effect of water stress.
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Palavras-chave
Acumulação de nitrato, Componentes fenólicos, Estresse hídrico, Fotossíntese, Massa seca, Reidratação, Prolina, Dry matter, Nitrate accumulation, Phenolic compounds, Photosynthesis, Proline, Rehydration, Water stress