Effects of Hydroponic Solution EC, Substrates, PPF and Nutrient Scheduling on Growth and Photosynthetic Competence During Acclimatization of Micropropagated Spathiphyllum plantlets

Abstract

In vitro regenerated shoots of Spathiphyllum from bioreactor were hydroponically cultured for 30 days. The response of plant growth and photosynthesis to different substrates, photosynthetic photon flux (PPF), nutrient scheduling and electrical conductivity (EC) of hydroponic solution were studied. The best plant growth response was observed in perlite based substrates with moderate PFF (70-100lmol m À2 s À1 ). Highest fresh weight, dry weight, shoot length, root length, root number and photosynthetic characteristics (chlorophyll, carotenoids and Fv/Fm) was observed in continuous immersion system. Plant growth responses, photosynthetic rate, stomatal conductance and transpiration rate were also found to be affected by EC levels. The optimum EC of a balanced nutrient solution was recorded as 1.2 dS m À1 . Photosynthetic activity was also characterized in terms of photochemical efficiency using measurements of chlorophyll fluorescence. Fv/Fm (it is a measure of the intrinsic or maximum efficiency of PSII i.e. the quantum efficiency if all PSII centers were open) also decreased significantly in plants grown under higher EC level; a decrease in this parameter indicates down regulation of photosynthesis or photoinhibition. Antioxidant defense enzymes such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR) significantly elevated in the leaves and roots of plantlets at higher EC levels. This increase could reflect a defense response to the cellular damage provoked by higher EC levels in the nutrient solution.

Aclimatização de Brassavola tuberculata com a utilização de ANA em diferentes substratos

“…Sabe-se que a eficiência, no processo de aclimatização, pode ser aumentada com o estímulo da formação de raízes (Dewir et al, 2005) em plantas oriundas do cultivo in vitro. As raízes das orquí-deas além de serem responsáveis pela fixação no substrato (Taiz & Zeiger, 2008), também possibilitam a absorção de água, reduzindo, assim, os efeitos da dessecação e aumentando a probabilidade de sobrevivência das plantas (Souto et al, 2010).…”

Photosynthetic and biochemical characterization of in vitro-derived African violet (Saintpaulia ionanthaH. Wendl) plants to ex vitro conditions

“…, was optimal for the acclimatization of Spathiphyllum plantlets (Dewir et al 2005). The exposure of Calathea louisae and Spathiphyllum floribundum plantlets to high irradiance (300 μmol m −2 s −1 ) immediately after transplantation caused photoinhibition and even Chl photobleaching (Van Huylenbroeck et al 1995).…”

“…Maximal variable fluorescence (F v = F m -F 0 ) and the photochemical efficiency of PSII (F v /F m ) were calculated for dark-adapted leaves (Dewir et al 2005). Four plants were randomly selected and measurements were made on fully expanded young leaves using a standard leaf chamber.…”

“…However, an incremental increase in Chl content has been reported in many plant species after ex vitro transplantation (Pospíšilová et al 1988 . The decrease in this parameter indicates the down regulation of photosynthesis or photoinhibition (Matysiak 2004;Dewir et al 2005). Kozai and Sekimoto (1988) reported that high PPFD was essential for improving the efficiency of photosynthesis.…”

“…After ex vitro transfer, these plantlets might easily be impaired by sudden changes in environmental conditions, and so a period of acclimatization to correct abnormalities is needed (Pospíšilová et al 1999). As a consequence, plants raised in vitro are grown in environmentally controlled growth chambers or greenhouses and factors such as light, temperature, and humidity are gradually enhanced for their step-by-step acclimatization (Pospíšilová et al 1999;Hazarika 2003;Dewir et al 2005). In order to increase growth and to reduce the mortality of plantlets at the acclimatization stage, research has focused on the control of environmental factors which optimizes the survival of plantlets (Hazarika 2003;Dewir et al 2004Dewir et al , 2005.…”