Photosynthetic characteristics involved in adaptability to Karst soil and alien invasion of paper mulberry (Broussonetia papyrifera (L.) Vent.) in comparison with mulberry (Morus alba L.)

Abstract

Unlike mulberry (Morus alba, M.a.), paper mulberry (Broussonetia papyrifera, B.p.) can acclimate to Karst soil and incline to alien invasion. The photosynthetic parameters, diurnal changes of carbonic anhydrase, and chlorophyll fluorescence induction, and water potential were measured on sunny days (SD) and cloudy days (CD). Photosynthetic midday depression occurred in B.p. but not in M.a. The irradiance-and CO 2 -saturated photosynthetic rates of B.p. were significantly higher than those of M.a. There was no significant difference in water use efficiency between the two species on a SD. The maximum fluorescence, maximum quantum yield, photochemical quenching, and relative electron transport rate in the leaves of B.p. were much higher than those in M.a. The activity of carbonic anhydrase (CA) of B.p., on either an SD or a CD, was much greater than that of M.a. Higher transpiration rate (E) and net photosynthetic rate (P N ) of B.p. resulted in the lack of water in mesophyll cells. Although a higher CA activity of B.p. supplied both water and CO 2 for the photosynthesis of mesophyll cells, water in mesophyll cells was the factor limiting photosynthesis, and the intercellular CO 2 concentration of B.p. was high and stable.Additional key words: carbonic anhydrase; chlorophyll a fluorescence; mulberry; photochemical and non-photochemical quenching; species differences; stomatal conductance; transpiration rate; water potential.--Paper mulberry (Broussonetia papyrifera (L.)Vent.; B.p.) and mulberry (Morus alba L.; M.a.), perennial tree species belonging to Moraceae, are characterized by higher growth rate and greater adaptability to adverse environments than other species in this family (Zhang et al. 1998. They have been cultivated extensively in East, Central, and South Asia for papermaking, silk and timber production, and medical materials (Qin et al. 1999, Ouyang andChen 2003).Many investigations have addressed such physiological aspects as changes of peroxidase, esterase isozyme activities, and endogenous indole-3-acetic acid during cambial activity, the regeneration from leaf mesophyll protoplasts, and the accumulation of dry matter of each organ and various parts in paper mulberry (Oka and Ohyama 1985, Cui et al. 1995a,b, 1999, Dai 1995. Karst areas often suffer from water stress because of the unique geo-environment (Zhou et al. 2003). Therefore, drought tolerance is vital to the plants in the Karst area. Recent studies have also shown that this plant species, which is native to East Asia, has become an invader on several continents and in more than dozen countries (Ghersa et al. 2002, Morgan andOverholt 2005).Certain physiological changes of mulberry in response to water stress, high temperature, and toxic effects of heavy metals have been studied (

Rhizosphere calcareous soil P-extraction at the expense of organic carbon from root-exuded organic acids induced by phosphorus deficiency in several plant species

“…Therefore, Bp was able to obtain a great amount of available P from rhizosphere soil under P deficiency via complexation with OA, MA and CA. This explains a previous observation that Bp has a higher net photosynthetic rate than Ma in the Karst environment (Wu et al 2009). In herbaceous cruciferous plants, the amount and percentage of root-exuded organic acids in Ov was higher than those in Bn.…”

Root-exuded malic acid versus chlorophyll fluorescence parameters in four plant species under different phosphorus levels

“…P deficiency had small destroy in PS II reaction centers in B. papyrifera and O. violaceus unlike in M.alba and B.napus. This conclusion is similar to the variation of the net photosynthetic rate: B. papyrifera is higher than M.alba (Wu et al, 2009), and O.violaceus is higher than B. napus (Wu et al, 2007). This finding indicates that B.papyrifera and O.violaceus have a stronger adaptability to a low-P environment than M.alba and B.napus.…”

Comparative ecophysiological responses to drought of two shrub and four tree species from karst habitats of southwestern China

“…Many adaptive responses to drought stress of karst plants have been reported, including photosynthetic performance (Huang et al 2006;Zhang et al 2007;Wu et al 2009;Zhu et al 2009;Liu et al 2010), leaf anatomical characteristics (Deng et al 2004;Rong et al 2005), xylem hydraulic traits (Chen et al 2009), osmotic adjustments (Liu et al 2003;Wei et al 2005), and antioxidant enzymes (Liu et al 2003;Zhu et al 2009). However, these studies have mainly focused on tree species, and how shrub species adapt to drought stress in the karst habitats is still unclear.…”