water flows into the source end of a seive tube because <\/p>\n\n\n\n
a. sucrose has been actively transported into the sieve tube, increasing solute concentration <\/p>\n\n\n\n
b. the companion cell of a seive tube actively pumps in water <\/p>\n\n\n\n
c. sucrose has been transported out of the seive tube by active transport<\/p>\n\n\n\n
d. water pressure outside the sieve tube forces in water<\/p>\n\n\n\n
The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n Correct Answer: A. sucrose has been actively transported into the sieve tube, increasing solute concentration<\/strong><\/p>\n\n\n\n Water flows into the source end of a sieve tube due to a process called pressure flow<\/strong> or mass flow<\/strong>, which is explained by the pressure-flow hypothesis<\/strong>. This hypothesis describes how sugar is transported in the phloem, which includes sieve tubes and companion cells.<\/p>\n\n\n\n At the source<\/strong> (usually a leaf where photosynthesis happens), sucrose is actively transported<\/strong> from the companion cells into the sieve tube elements. This active transport increases the concentration of solutes inside the sieve tube. Since water moves from areas of low solute concentration to areas of high solute concentration by osmosis, water from the nearby xylem<\/strong> enters the sieve tube. This inflow of water increases the turgor pressure<\/strong> inside the sieve tube at the source end.<\/p>\n\n\n\n The increased pressure at the source end causes the sugary sap to flow through the phloem toward the sink<\/strong>, which is a part of the plant where sugar is used or stored, such as roots, fruits, or developing leaves. At the sink, sucrose is actively or passively removed from the phloem, which lowers the solute concentration. Water then exits the phloem, reducing pressure at that end. The pressure difference between the source and the sink drives the bulk flow of the sugar solution through the sieve tubes.<\/p>\n\n\n\n The companion cells help with the loading and unloading of sucrose but do not directly pump water. Water is not forced in by pressure from outside the sieve tube, and sucrose is not transported out at the source. Therefore, option A is correct<\/strong> because it identifies the primary event that increases solute concentration and causes water to enter the sieve tube by osmosis.<\/p>\n","protected":false},"excerpt":{"rendered":" water flows into the source end of a seive tube because a. sucrose has been actively transported into the sieve tube, increasing solute concentration b. the companion cell of a seive tube actively pumps in water c. sucrose has been transported out of the seive tube by active transport d. water pressure outside the sieve […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-39309","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/39309","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=39309"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/39309\/revisions"}],"predecessor-version":[{"id":39310,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/39309\/revisions\/39310"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=39309"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=39309"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=39309"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}