EFFECT OF MINIMUM SOIL TEMPERATURE ON DIFFERENTIAL DISTRIBUTION OF CYPERUS ROTUNDUS AND C. ESCULENTUS IN THE UNITED STATES*

Abstract

Tbe response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution oi'CyPerus esculentus L. (yellow nuUedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968-69 in the field at Urbana, Illinois. Less than 10% oiC. rotundus tubers survived at 2^0 for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to -2''C for 4 h or longer killed 50% of C. rotundus tubers, whereas -Go'G was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival oi' C. esculentus tubers in soil whieh frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why tlie species is restricted to the southeastern and southwestern regions of the U.S.A. L'Infiuence de la temperature du sol sur la repartition dijfirentielle de Gyperus rotundus et de Cyperus esculentus aux Etats-Unis R6sum£. La reaction des bulbes de Cyperus esculentus L. et de Cyperus rotundus L. aux basses temperatures a ete ^tudi^e pour obtenir des donnces fondles sur la physiologic quant k la repartition difF^rentielle de ces deux especes aux Etats-Unis, Seuls les bulbes dc C. esculentus sm-v^eurent au champ aprte l'hiver 19G8-69 k Urbana, Illinois. Moins de 10% des bulbes de C. rotundus surv^ctirent k 2°C pendant 12 semaiiies, alors que plus de 95% des bulbes de C. esculentus surv^curent k ee traitcment. Des expositions il -2°C pendant quatre heures ou plus tu^rent 50% des bulbes de C. rotundus, alors qu'il fallut -6,5°G pour tuer 50% des bulbes de C. esculentus. La pri^senee de C. rotundus est Uniitde aux regions oij le sol gele rarement, cependant que C. esculentus se reneontre dans les regions ou les temperatures du sol s'abaissent souvent au-dessous du point dc congelation. La survivance de bulbes de C. esculentus dans les sols qui gdent frequeniment peut etre une explication de sa repartition tr^s etendue. La mort des bulbes de C. rotundus dans lea sols qui gclent peut etre la raison principale de la localisation de cette espece restreinte atix regions du Sud-est et du Sud-ouest des U.S.A.Der Einjluss der Bodentemperatur auf die unUrschiedliche Verbreitung von Gyperus rotundus und C. esculentus in den Vereinigten Staaten,

Differential Cold Tolerance, Starch, Sugar, Protein, and Lipid of Yellow and Purple Nutsedge Tubers

“…Only 8% of the yellow nutsedge 'G' tubers were viable after the winter. These responses to cold agree with other research on differences in tuber survival between purple and yellow nutsedges (20). In addition, these data show intraspecific differences within the yellow nutsedges in the tuber response to cold.…”

“…Differences in response to the cold can explain the differential distribution of these two species (20 The polar lipids from leaf extracts were isolated by TLC on plates developed in petroleum ether-diethyl ether-ethanolamine (58:30:12). In this system, the polar lipids remained at the origin, whereas the pigments moved to the solvent front.…”

Yellow and purple nutsedges survey in the southeastern Buenos Aires Province, Argentina

“…Daily soil mean temperatures during the coldest month in the surveyed area remain between 3 o C and 6 o C (Boletín Agrometeorológico, 1988Agrometeorológico, , 1989Agrometeorológico, ,1991Agrometeorológico, , 1992. Even though temperatures are not as low as those reported by Stoller (1973) as limiting for species of nutsedge distribution in the USA, they make difficult the survival of tubers of purple nutsedge under field conditions, specially of those wintering near the soil surface and more exposed to frosts.…”

“…Stoller (1973) found that tubers of purple nutsedge did not survive soil temperatures of 2 o C during 12 weeks, while tubers of yellow nutsedge survived after receiving the same treatment. Daily soil mean temperatures during the coldest month in the surveyed area remain between 3 o C and 6 o C (Boletín Agrometeorológico, 1988Agrometeorológico, , 1989Agrometeorológico, ,1991Agrometeorológico, , 1992.…”

Efeito da palha de cana-de-açúcar e do tamanho de tubérculos no desenvolvimento da tiririca (Cyperus rotundus L.).

“…Entretanto, esse método de controle só deve ser realizado nos meses em que não ocorre precipitação pois seis dias após a aração, se fosse dada condição para que a tiririca germinasse, 13,7% dos tubérculos ainda estariam viáveis e apenas dezesseis dias após, nenhum tubérculos seria viável (Day & Russell, 1955) O maior problema em utilizar esse controle é a necessidade de operações muito freqüentes e que demandam tempo e dinheiro (Victória Filho, 1985). Além disso, segundo Smith & Mayton (1942) (Smith & Mayton, 1942) mas estes já foram observados até a profundidade de 0,40 m (Stoller, 1973). Bhardwaj & Verma (1968) A tiririca apresenta forte dominância apical e embora esta seja o principal fator que controla a dormência do tubérculo, a umidade do solo, a luz, o teor de oxigênio e a temperatura influenciam o processo de emissão de brotações.…”