Although the transporting tissue became thus finally identified in the 18th and

Question

Although the transporting tissue became thus finally identified in the 18th and early 19th
centuries, the pathway problem lingered on at the microscopic level well into the second half of
the 19th century. There were lively disputes on whether the lumen of a conducting xylem
element (a tracheid or a trachea) is filled with water, with air or with a sequence of air bubbles
interspersed with water (a so-called "Jamin chain"). According to their opinion on this problem,
various authors suggested different routes for water ascent. Water was thus assumed to move in
the lignified cell walls of air-filled conduits by Unger, Sachs and Pfeffer, or to be transported in
the lumen by Boehm, Strasburger and Schwendener, among others. De Candolle and and some
followers even credited intercellular spaces with a role in transport

The anatomical arguments gradually became inseparable from the task of identifying a suitable driving force for water movement. In a way, the idea that living cells should play a major role in lifting and moving the water seemed natural enough; the "vitalists" were however neither able to identify living cells prominently involved in water transport nor to suggest plausible mechanisms for their action. Nevertheless they kept fighting against the "physicists" and their cohesiontension theory (CTT) well into the 20th century. Great names in plant physiology among the vitalists, such as S. Schwendener and W. Pfeffer, were later followed by A. Ursprung and others as champions in the fight for an essential role of the protoplasm in water ascent. Indeed, even J. Joly and H. H. Dixon, two of the earliest protagonists of the CTT, preserved some "vitalist" convictions for a long time.

The sight of only the abstract prompted Eugen Askenasy (Professor of Botany in Heidelberg) to reveal his ideas which he had nurtured for a long time. Askenasy had not yet published anything on the water relations of plants till then as his main interest being the taxonomy of marine algae. However, in December 1894 and February 1895 he published in the Verhandlungen des Naturhistorisch-Medicinischen Vereins zu Heidelberg, Neue Folge 5, a paper showing a remarkable grasp of the whole topic and theoretical ideas very similar to those in Dixon and Joly´s full paper. What were these new ideas? The most important common feature to both papers was the identification of the cell walls of parenchyma cells, whether living or dead, as the sites where surface tensions develop due to the transpiration of water. Both papers emphasized that a moist cell wall is impermeable to air, so that even at negative pressures air cannot be sucked into conducting elements. A somewhat "vitalist" idea in Askenasy´s paper was the (rather complicated and unnecessary) assumption that the increased surface tension created by transpiration should be first used for removing water from the protoplast, and only the "osmotic force" created should exert a pulling action on the water threads in the conducting elements held together by cohesion. This idea was taken up a short time later in a paper by Dixon.

“Vitalists” believed (erroneously) that:  

Explanation / Answer

b)Living cells are responsible for lifting water up trees.

Note :- water is conducted through xylem which is a dead tissue.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.