Effects of NaCl and Iso-osmotic PEG6000 on Seedling Photosynthesis and Growth of Pongamia pinnata, Casuarina equisetifolia, and Thespesia populnea
Date Issued
2009
Date
2009
Author(s)
Chi, Pei-Chen
Abstract
Seedlings of Pongamia pinnata, Casuarina equisetifolia and Thespesia populnea grown in plastic pots were subjected to (1) NaCl (S1:0.7 %, S2:1.4 %, S3:2.8 %),(2) PEG6000, iso-osmotic to NaCl solution(P1:-0.555 MPa, P2:-1.109 MPa, P3:-2.248 MPa) and (3) well-watered treatment “C”, respectively. After 6 weeks, the photosynthetic rate (Pn), stomatal conductance (gs), cholorophyll fluorescence, content of pigments and growth were measured.he trend of xylem water potential(Ψxyl) in treatments is C > S1≒P1> S2≒P2> S3≒P3 in the three species. Leaf area decreased with decreasing water potential, and the photosynthetic rate also showed this trend. In PEG treatment, Pn decreased with decreasing solution osmotic potential and was lower than iso-osmotic NaCl treatments. The gs of the three species decreased by decreasing water potential, and the decreasing gs in PEG treatments was more severe than iso-osmotic NaCl. Fv/Fm did not differ significantly among treatments except P3 treatment. After PEG and NaCl treatments, the decrease in Pn largely resulted from the decrease in gs. Except P3, photosystem II (PSII) did not differ significantly among other treatments. The damages caused by PEG and NaCl were due to osmotic stress similiar to water stress. It should be noted that seedlings irrigated with iso-osmotic PEG were damaged than those treated with NaCl.
Subjects
Pongamia pinnata
Casuarina equisetifolia
Thespesia populnea
Net photosynthetic rate
Chlorophyll fluorescence
Type
thesis
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