HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nicolodi, C. Articles by Di Marco, G. Search for Related Content PubMed Articles by Nicolodi, C. Articles by Di Marco, G. Agricola Articles by Nicolodi, C. Articles by Di Marco, G.

Water Status Effects on Net Photosynthesis in Field-Grown Alfalfa

Inst. of Plant Biochemistry and Ecophysiology, Nat. Res. Counc., 00016 Monterotondo Scalo, Rome, Italy

^* Corresponding author.

Net photosynthesis (Pn) typically declines with drought. Partitioning of this decline into stomatal and nonstomatal factors determines the seasonal performance and stress adaptation of the leaves. Here stomatal and nonstomatal limitations to Pn in alfalfa (Mediago sutiva L.) are evaluated to determine their relative importance during drought. Photosynthesis of the upper leaves of irrigated and nonirrigated alfalfa (cv. Sabina) was determined in 1985 and 1986 during spring regrowth. In both years, Pn was inhibited more than 35% in nonimgated compared with irrigated plants, which had higher leaf water potential. Internal CO₂ partial pressure (pi) indicated that stomatal limitation was not the only reason for reduced Pn, stomatal and nonstomatal effects were about equally important in the inhibition of Pn in leaves of nonirrigated plants in 1986. In vitro ribulose- 1,s-bisphosphate carboxylase activity (RuBPCO) per unit leaf area was higher in the nonirrigated treatment, suggesting that the enzyme was not responsible for the nonstomatal component of inhibition of Pn. In 1986, O₂ evolution, measured in detached leaves with saturating CO₂, was lower in the nonirrigated treatment compared to the irrigated one, implying that limitations to ribulose-1,Sbisphosphate (RuBP) regeneration may play a significant role. The carbon isotope composition of total leaves of plants collected at the end of the experiment in 1985 and 1986 showed a lower discrimination against ¹³C in nonirrigated compared with the irrigated leaves, indicating a reduced conductance to C0₂ transfer. It is concluded that both stomatal and nonstomatal mechanisms contributed to reduced Pn in droughted alfalfa.

Received for publication September 28, 1987.

This article has been cited by other articles:

				G. W. Powell and E. W. Bork Simulated Aspen Understory Microclimate Effects on Alfalfa Growth Agron. J., August 17, 2005; 97(5): 1361 - 1366. [Abstract] [Full Text] [PDF]

				J. FLEXAS and H. MEDRANO Drought-inhibition of Photosynthesis in C3 Plants: Stomatal and Non-stomatal Limitations Revisited Ann. Bot., February 1, 2002; 89(2): 183 - 189. [Abstract] [Full Text] [PDF]