PJB-2018-655
Effects of irradiance on growth and morphophysiology in Catalpa bungei plantlets
Quan Qiu, Junhui Wang, Na Lin, Yan Su, Jianwei Ma, Jiyue Li and Qian He
Abstract
With the aim of examining the effect of irradiance on growth and morphophysiology in Catalpa bungei, and its acclimation strategy to different shade intensity treatments, a pot experiment was conducted to determine the growth, morphological, and physiological parameters of C. bungei clone 008-1 plantlets under high (HI), medium (MI), and low (LI) irradiance levels, i.e. at approximately 80, 50, and 30% of full sunlight, respectively. Irradiance provoked significant and varied changes in phenotypic plasticity index (PPI) values for growth (ca. 0.44), morphology (ca. 0.37), and physiology (ca. 0.28). Shade treatments (MI and HI) reduced growth, biomass yield, crown leaf area per plant, expansion rate of newly emerged leaves and their size at the end of expansion (length, width, and area), specific leaf weight, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, instantaneous water use efficiency, and δ13C values, whereas specific leaf area (SLA), leaf chlorophyll concentration, and leaf nitrogen (N) concentration were greatly decreased. MI did not affect maximum quantum yield of PSII (Fv/Fm) values; however, LI induced a significant decrease in Fv/Fm. Shaded plantlets generally had higher or similar non-structural carbohydrate (NSC) concentrations than HI plantlets. Overall, growth traits linearly decreased with decreasing irradiance, but morphological and physiological traits exhibited different dynamic trends. Our results showed that C. bungei coped with shade through morphophysiological adjustments, i.e. increasing SLA, leaf chlorophyll content, and NSC reserves; however, shade (ca. 30–50% full sunlight) still induced a significant reduction in plantlet growth due to photosynthesis restriction (MI: stomatal closure; LI: stomatal closure and lower photosystem II efficiency) and changes in NSC allocation strategy, preferring to maintain metabolism and survival rather than growth investment.
To Cite this article:
Qiu, Q., J. Wang, N. Lin, Y. Su, J. Ma, J. Li and Q. He. 2020. Effects of irradiance on growth and morphophysiology in Catalpa bungei plantlets. Pak. J. Bot., 52(6): DOI: http://dx.doi.org/10.30848/PJB2020-6(23)
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