Water status and gas exchange of umbu plants (Spondias tuberosa Arr. Cam.) propagated by seeds and stem cuttings

Abstract

-The experiment was carried out at the Embrapa Semi-Árido, Petrolina-PE, Brazil, in order to study the physiological responses of umbu plants propagated by seeds and by stem cuttings under water stress conditions, based on leaf water potential and gas exchange measurements. Data were collected in one-year plants established in pots containing 30 kg of a sandy soil and submitted to twenty-day progressive soil water deficit. The evaluations were based on leaf water potential and gas exchange data collection using psychrometric chambers and a portable infra-red gas analyzer, respectively. Plants propagated by seeds maintained a significantly higher water potential, stomatal conductance, transpiration and photosynthesis under decreasing soil water availability. However, plants propagated by stem cuttings were unable to maintain a favorable internal water balance, reflecting negatively on stomatal conductance and leaf gas exchange. This fact is probably because umbu plants propagated by stem cuttings are not prone to formation of root tubers which are reservoirs for water and solutes. Thus, the establishing of umbu plants propagated by stem cuttings must be avoided in areas subjected to soil water deficit. Index terms: water potential, stomatal conductance, transpiration, photosynthesis, root tubers. ESTADO HÍDRICO E TROCAS GASOSAS DE UMBUZEIROS (Spondias tuberosa Arr. Cam.) PROPAGADOS POR SEMENTES E ESTAQUIARESUMO-O experimento foi realizado na Embrapa Semi-Árido, Petrolina-PE, Brasil, objetivando estudar as respostas fisiológicas de umbuzeiros propagados por sementes e por estaquia, sob condições de deficiência hídrica. Os dados foram coletados em plantas com aproximadamente um ano de idade, estabelecidas em vasos contendo 30 kg de solo de textura arenosa e submetidas a déficit progressivo de água, durante 20 dias. As avaliações foram realizadas, tomando-se como base o potencial hídrico foliar e as trocas gasosas, monitorados com auxílio de câmaras psicrométricas e um analisador portátil de gás por infravermelho, respectivamente. As plantas propagandas por sementes mantiveram valores de potencial hídrico, condutância estomática, transpiração e fotossíntese significativamente maiores, sob condições decrescentes de disponibilidade de água no solo. Entretanto, plantas propagadas por estaquia foram incapazes de manter um balanço hídrico favorável, refletindo negativamente na condutância estomática e trocas gasosas. Estes resultados estão provavelmente associados ao fato de que o umbuzeiro propagado por estaquia dificilmente apresenta túberas em suas raízes, as quais são reservatórios de água e solutos. Dessa forma, o plantio de umbuzeiros propagados por estaquia deve ser evitado em áreas sujeitas à deficiência hídrica. Termos para indexação: potencial hídrico, condutância estomática, transpiração, fotossíntese, túberas.

<i>Spondias tuberosa</i> trees grown in tropical, wet environments are more susceptible to drought than those grown in arid environments

“…In this study, we showed that, during the period when the water stress was most severe, i.e., November, the photosynthetic rates of the tropical arid plants were significantly higher than the rates in the tropical wet plants, an effect that was strongly shifted at the beginning of the rainy season, which is the opposite to what should be expected for trees growing in a wet environment. Some investigators previously reported that S. tuberosa can maintain its Ψpd at a relatively constant level during the beginning of the dry season (Lima Filho, 2001;Lima Filho, 2004;Lima Filho, 2007;Lins Neto et al, 2012). A possible explanation for this result is that the umbu tree reduces its stomatal conductance in response to drought early in the morning, resulting in a dramatic decline in plant water loss and assuring (Lima Filho and Silva, 1988).…”

“…Tropical plants growing under water stress exhibit modifications in photosynthetic processes, including disruptions in the stomatal control of the leaf gas exchange (Arcoverde et al, 2011;Lawlor and Tezara, 2009;Lima Filho, 2007;Pompelli et al, 2010a;Santos et al, 2013), alterations in chlorophyll fluorescence kinetics (Faraloni et al, 2011;Maxwell and Johnson, 2000), damage to photosynthetic membranes (Krieger-Liszkay, 2005), changes in the carbohydrate status (Chimenti et al, 2002;Silva et al, 2010), and others. The water stress-induced limitation of net photosynthesis (P N ) may cause damage to the plant with exposure to excess irradiance; if this energy is not safely dissipated, it may cause an overreduction of the reaction centers and increased production of reactive oxygen species (ROS) in the chloroplasts, leading to photosystem PSII damage (Smirnoff, 1995).…”

“…These investigators suggested that the root tubers may act as an important source of water under stress conditions. However, the aforementioned studies (Lima Filho, 2001;Lima Filho, 2004;Lima Filho, 2007) only describe the gas exchange of umbu trees under semiarid conditions and the importance of tubers in helping plants avoid stress.…”

Spondias tuberosa Arruda (Anacardiaceae), a threatened tree of the Brazilian Caatinga?

“…S. tuberosa forms root-tubers, which are able to store water, minerals, and organic solutes (Cavalcanti et al, 2010;Duque, 2004;Epstein, 1998;Lima, 1996). This adaption permits its survival during the dry season (Cavalcanti et al, 2010;Silva et al, 2008), and to initiate the flowering and leaf flush before onset of the wet season (Lima Filho, 2007;Machado et al, 1997). Due to these early signs of life in the otherwise dormant Caatinga at the end of the dry season, the tree is worshipped by indigenous tribes in spiritual rituals (Monteiro, 2007).…”

Superação da dormência de sementes e crescimento inicial de plântulas de umbuzeiro no submédio do São Francisco

“…Além disso, possui a capacidade de perder as folhas após o período das chuvas, no intuito de economizar água e nutrientes, o umbuzeiro passa por um estado de dormência, com os xilopódios desempenhando papel importante na sobrevivência da espécie (Santos, 1997). A abscisão total das folhas do umbuzeiro ocorre cerca de 1 a 2 meses após a última precipitação e o lançamento das primeiras flores pode ser observado ainda sob condições de seca, apresenta sistema radicular especializado formado por raízes longas, espalhadas horizontalmente, próximas à superfície do solo (Lima Filho, 2011).…”