The effects of severity of defoliation and soil moisture stress on Desmodium intortum

1971 ◽  
Vol 11 (52) ◽  
pp. 521 ◽  
Author(s):  
BC Imrie

The responses of five introductions and one cultivar of Desmodium intortum to two defoliation intensities under stress and non-stress soil moisture regimes were studied in a pot experiment. Both heavy defoliation and moisture stress reduced yield. Significant line X defoliation interactions occurred, including differences among the component lines of the cultivar Greenleaf. Evidence was found that genetic shift has occurred in Greenleaf in the direction of the lower yielding components which were more adversely affected by severe defoliation. The wisdom of releasing mixtures of 'pure' lines as commercial varieties of perennial pasture species is questioned.

1965 ◽  
Vol 45 (5) ◽  
pp. 419-427 ◽  
Author(s):  
E. N. Larter ◽  
M. Samii ◽  
F. W. Sosulski

A study was made of the effects of (2-chloroethyl) trimethylammonium chloride (CCC) applied to the varieties Parkland and Hannchen barley grown under controlled environmental conditions and predetermined soil moisture regimes. When applied to seedlings as either a soil drench or as a foliar spray, CCC retarded internode elongation thereby significantly reducing the height of plants as measured at maturity. A varietal difference in the response to a given treatment was evident with Parkland being more sensitive than Hannchen. Moreover, measured in terms of growth responses, application of CCC as a soil drench was more effective than as a foliar spray.Treatments in the range of 10−1–10−4 M significantly increased tiller number and seed yield on plants grown under a high moisture regime (daily watering). Under restricted soil moistures, however, neither grain yield nor plant weights (tops) were affected by CCC treatment. Treated plants grown under soil moisture stress used less water per unit weight of dry matter than did untreated plants.


Author(s):  
Jagbir Singh ◽  
S. K. Varma ◽  
J. N. Bhatia ◽  
Lekh Raj

Soil moisture stress and salinity resulted reduction in almost all the growth, yield and yield attributes in mustard var. RH-30. Salinity behaved similarly to soil moisture stress and the magnitude of reduction increased with the increase in their level accordingly. Chloride type of toxicity was found to be more harmful than that of sulphate toxicity. The results obtained in the present study suggested that maintenance of wetter irrigation under salinity could go a long way in maximizing the crop production in mustard


2009 ◽  
Vol 6 (8) ◽  
pp. 1423-1444 ◽  
Author(s):  
T. Keenan ◽  
R. García ◽  
A. D. Friend ◽  
S. Zaehle ◽  
C. Gracia ◽  
...  

Abstract. Water stress is a defining characteristic of Mediterranean ecosystems, and is likely to become more severe in the coming decades. Simulation models are key tools for making predictions, but our current understanding of how soil moisture controls ecosystem functioning is not sufficient to adequately constrain parameterisations. Canopy-scale flux data from four forest ecosystems with Mediterranean-type climates were used in order to analyse the physiological controls on carbon and water flues through the year. Significant non-stomatal limitations on photosynthesis were detected, along with lesser changes in the conductance-assimilation relationship. New model parameterisations were derived and implemented in two contrasting modelling approaches. The effectiveness of two models, one a dynamic global vegetation model ("ORCHIDEE"), and the other a forest growth model particularly developed for Mediterranean simulations ("GOTILWA+"), was assessed and modelled canopy responses to seasonal changes in soil moisture were analysed in comparison with in situ flux measurements. In contrast to commonly held assumptions, we find that changing the ratio of conductance to assimilation under natural, seasonally-developing, soil moisture stress is not sufficient to reproduce forest canopy CO2 and water fluxes. However, accurate predictions of both CO2 and water fluxes under all soil moisture levels encountered in the field are obtained if photosynthetic capacity is assumed to vary with soil moisture. This new parameterisation has important consequences for simulated responses of carbon and water fluxes to seasonal soil moisture stress, and should greatly improve our ability to anticipate future impacts of climate changes on the functioning of ecosystems in Mediterranean-type climates.


2011 ◽  
Vol 63 (6) ◽  
pp. 392-392 ◽  
Author(s):  
Anil Gunaratne ◽  
Upul Kumari Ratnayaka ◽  
Nihal Sirisena ◽  
Jennet Ratnayaka ◽  
Xiangli Kong ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document