Vergara - 1976 - Physiological and morphological adaptability of ri

cunmrs INFLUENCE ON PHOTOSYNTHESIS AND RESPIRATION 241
Table 3. Change in tho distributions of summer woods with different photosynthetic
pathway as affected by soll moisture (composed by I. Tanalta from the data of Aral et al..
1955}.
Photosynthetic
Water
pathway Weed Submergence saturated Upland
C. Type Elatlne orients/rs Makino 155g 0g 0g
Monochwia vagina/is Presl. 0J0 0 9
Cyperus difformrs L. 0.35 0 0
Dopatcuium junoeum Hamrlt. 1.50 + 0
Linderme pyxrdana All 0.20 + 0
Eleocharls aciculeris R Br. 0.60 + 0
Rotsla indies var. ulfginosa tMrq.)
Koehne 355 0.05 0
Ertocaulon sieboldtianum Shad. 0.20 0.15 0
Poe ecroleuca Steud. 0 0.25 0.05
Polygonum bluntel Meisn. 0 1.20 2.20
Acalypha auslralis L. 0 0.05 0.50
Chenopodrum album L 0 1.10
Subtotal 8.65 1.70 3.85
(39) (5) t7)
c, Type Echincchloa mus-gall!" Beam. var. 0T0 T95 5.75
oryzicola Ohwi.
Cyperus mrcroira Steud. 0.25 3.90 4.55
Fimbristj/lis Ilttoralis Gaudich. 0.10 1.10 1.55
Amaranthus blitum L. 0 0.10 0.50
Echlrrochloa crus-gallr Beauv. var.
platloorla Ohwi. 0 3.20 5.55
Setarra viridls Beauv. 0 925 10.10
Digitalis crliaris Pers. 0 3.60 25.35
Portulaca oleracea L. 0 0.35
Subtotal 1.05 29.10 54 00
(11) (94) (93)
Total (C, + C. Type) 9.70 30.80 57.85
(100) (100) (100)
Note Submergence: 6 cm l|'l standing water depth, Water saturated 80-90% of maximum moisture
capacity. Upland 40-60% of maximum moisture capacity
Figures represent the total dry weights oi each weed in an area of 90 crn ~ 90 cm
The anaerobic substance in submerged soil are removed by aeration. Myasaka
(I961) reported that drainage at late tillering stage brought about an increase in
photosynthesis and a decrease in respiration during the ripening period.
Submcrgcncc may have a large influence on photosynthesis of a rice population
through controlling C, weeds which compete strongly with the rice plant.
The tropical climate uith high temperature and high solar radiation is more
favorable for some needs than for rice. It is well known that poor cultural management
of rice fields rapidly leads to severe infestations by Echirmchloa arm;-
galli, Cvpenrs microira, Digilaria ciliaris, and Setaria viridis. They are common
summer weeds belonging to C, species.
The high photosynthetic capacity of these weeds under high temperature and
high light intensity makes them very efficient competitors in tropical and temperate
regions during the summer. Efficient use of water is another distinguishing
characterihtic of C, species. Black et al. (1969) compared water requirements
for weeds and crops with different CO, fixation pathurays from the data of
Shantz and Picmciscl (1927). The data indicated that C, species required about
half as much “tater to produce lg of dry matter as C, species did. Therefore,