Plant and Soil

, Volume 185, Issue 1, pp 137–149

Effect of soil drying on growth, biomass allocation and leaf gas exchange of two annual grass species

  • Tibor Kalapos
  • Riki van den Boogaard
  • Hans Lambers
Regular Research Articles

DOI: 10.1007/BF02257570

Cite this article as:
Kalapos, T., van den Boogaard, R. & Lambers, H. Plant Soil (1996) 185: 137. doi:10.1007/BF02257570

Abstract

Influence of short-term water stress on plant growth and leaf gas exchange was studied simultaneously in a growth chamber experiment using two annual grass species differing in photosynthetic pathway type, plant architecture and phenology:Triticum aestivum L. cv. Katya-A-1 (C3, a drought resistant wheat cultivar of erect growth) andTragus racemosus (L.) All. (C4, a prostrate weed of warm semiarid areas). At the leaf level, gas exchange rates declined with decreasing soil water potential for both species in such a way that instantaneous photosynthetic water use efficiency (PWUE, mmol CO2 assimilated per mol H2O transpired) increased. At adequate water supply, the C4 grass showed much lower stomatal conductance and higher PWUE than the C3 species, but this difference disappeared at severe water stress when leaf gas exchange rates were similarly reduced for both species. However, by using soil water more sparingly, the C4 species was able to assimilate under non-stressful conditions for a longer time than the C3 wheat did. At the whole-plant level, decreasing water availability substantially reduced the relative growth rate (RGR) ofT. aestivum, while biomass partitioning changed in favour of root growth, so that the plant could exploit the limiting water resource more efficiently. The change in partitioning preceded the overall reduction of RGR and it was associated with increased biomass allocation to roots and less to leaves, as well as with a decrease in specific leaf area. Water saving byT. racemosus sufficiently postponed water stress effects on plant growth occurring only as a moderate reduction in leaf area enlargement. For unstressed vegetative plants, relative growth rate of the C4T. racemosus was only slightly higher than that of the C3T. aestivum, though it was achieved at a much lower water cost. The lack of difference in RGR was probably due to growth conditions being relatively suboptimal for the C4 plant and also to a relatively large investment in stem tissues by the C4T. racemosus. Only 10% of the plant biomass was allocated to roots in the C4 species while this was more than 30% for the C3 wheat cultivar. These results emphasize the importance of water saving and high WUE of C4 plants in maintaining growth under moderate water stress in comparison with C3 species.

Key words

C3 C4 relative growth rate Tragus racemosus Triticum aestivum water stress 

Abbreviations

A

photosynthetic rate

Ela

water loss on leaf area basis

gs

stomatal conductance for water vapour

IWR

inflorescence weight ratio

LA

total leaf area

LAR

leaf area ratio

LWR

leaf weight ratio

NAR

net assimilation rate

pi/pa

ratio of intercellular and atmospheric CO2 partial pressure

PPFD

photosynthetic photon flux density

PWUE

photosynthetic water use efficiency (A/gs)

RGR

relative growth rate

RW

total root dry weight

RWR

root weight ratio

SLA

specific leaf area

SWR

stem weight ratio

WUEB

water use efficiency of biomass production

ψleaf

leaf water potential

ψsoil

soil water potential

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Tibor Kalapos
    • 2
  • Riki van den Boogaard
    • 1
  • Hans Lambers
    • 1
  1. 1.Department of Plant Ecology and Evolutionary Biology Utrecht UniversityUtrechtThe Netherlands
  2. 2.Department of Plant Taxonomy and EcologyL. Eötvös UniversityBudapestHungary

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