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Mycorrhizae enhance plant nutrition mainly by:
a. Absorbing water and minerals through the fungal hyphae
b. Providing sugar to root cells, which have no chloroplasts
c. Converting atmospheric nitrogen to ammonia
d. Enabling the roots to parasitize neighboring plants
A mineral deficiency is likely to affect older leaves more than younger leaves if
a. The mineral is a micronutrient
b. The mineral is very mobile within the plant
c. The mineral is required for chlorophyll synthesis
d. The mineral is a macronutrient
Epiphytes are:
a. Fungi that attack plants
b. Fungi that form mutualistic associations with roots
c. Nonphotosynthetic parasitic plants.
d. Plants that grow on other plants.
Two groups of tomatoes were grown under laboratory conditions, one with humus added to the soil and one as a control without humus. The leaves of the plants grown without humus were yellowish (less green) compared with those of the plants grown in humus-enriched soil. The best explanation is that
a. The healthy plants used the food in the decomposing leaves of the humus for energy to make chlorophyll.
b. The humus made the soil more loosely packed, so water penetrated more easily to the roots.
c. The humus contained minerals such as magnesium and iron needed for the synthesis of chlorophyll.
d. The heat released by the decomposing leaves of the humus caused more rapid growth and chlorophyll synthesis.
The greatest difference in health between two groups of plants of the same species, one group with mycorrhizae and one group without mycorrhizae, would be in an environment
a. Where nitrogen-fixing bacteria are abundant
b. That has soil with poor drainage
c. That has hot summers and cold winters
d. In which the soil is relatively deficient in mineral nutrients
Some of the problems associated with intensive irrigation include all of the following except:
a. Soil salinization
b. Overfertilization
c. Land subsidence
d. Aquifer depletion.
