Question

Which of the following is a parasite?
a) Lemna
b) Arceuthobium
c) Spirodella
d) Wolffia

Answer 1

Hint: They are the smallest parasitic angiosperm having specialized water-conducting tissues. They parasitize a host of Pinaceae and Cupressaceae.

Complete answer:
Arceuthobium is the species of parasitic plants commonly called dwarf mistletoes. These plants have very reduced shoots and scaly leaves. They live under the host's bark in the bulk of the plant.

Characteristics of Arceuthobium plant:
1) These plants are dioecious i.e. individual plants are either male or female.
2) They consist of fruit that builds up hydrostatic pressure internally when ripe and shoots the single sticky seed up to speeds nearly 50 miles per hour.
3) The seeds are enclosed in a hygroscopic, sticky substance called viscin.
4) The smallest genus, A. minutissimum lives on Pinus wallichiana as its host, in the Himalayas.
5) Severe infection in these plants results in a reduction in tree growth, reduced seed, and cone development premature tree mortality, low wood quality, and increases the susceptibility of the host tree to pathogen or insect attack.
6) The interaction can be generalized as a source-to-sink relationship between dwarf mistletoes and their host.
7) They derived the majority of their nutrition from the host’s vascular tissues.
8) They possess a root-like endophytic system which is composed of primary and secondary haustoria. It invades but does not injure the xylem and phloem of the host.
9) They are phloem-deficient and make carbohydrates from their hosts by influences to the host phloem and ray parenchyma.

So, Option (b) is the correct answer

Note:
1) Dwarf mistletoes contain both chlorophyll a and chlorophyll b and the necessary mechanisms for photosynthesis but they have a low photosynthetic rate.
2) Haustorium is a rootlike structure that absorbs water or nutrients from host plants by growing into or around the host.