ICAR AICE-JRF/SRF (PhD) — Subject 59 Forestry · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersHow trees grow, take up water and nutrients, fix carbon, allocate it to wood, roots and reproduction, and respond to drought, heat, cold and shade.
In the exams: ICAR AICE-JRF 59 Unit 3 (growth substances) and Unit 12 (enhanced CO2); ICAR AIEEA-PG Group 09 Unit I plant physiology basics
How our questions for ICAR AICE-JRF/SRF spread across the units of Tree Physiology. Difficulty: 8 easy, 38 medium, 17 hard.
| Elevated CO2 and temperature effects on tree growth | 8 | |
| Water relations: transpiration, cohesion-tension, xylem embolism | 7 | |
| Respiration and carbon allocation | 7 | |
| Photosynthesis in trees: C3 pathway, light response, shade tolerance | 6 | |
| Dormancy, phenology and cold hardiness | 6 | |
| Mineral nutrition and mycorrhizae | 5 | |
| Cambial activity, wood formation and growth rings | 5 | |
| Plant growth regulators and their role in propagation | 5 | |
| Reproductive physiology: flowering, pollination, seed development | 5 | |
| Stress physiology: drought, salinity, flooding, frost | 5 | |
| Shoot and root growth patterns: determinate and indeterminate growth | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A branch has maximum conductivity 5.0 units; after drought its conductivity is 2.0 units. What is the percentage loss of conductivity (PLC)?
A. 60%
PLC = (5.0 − 2.0)/5.0 × 100 = 60%. 40% is the remaining conductivity; 250% inverts the ratio.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
P50 in a xylem vulnerability curve is:
C. The water potential at which 50% of conductivity is lost
P50 summarises embolism resistance; more negative P50 means more resistant xylem.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Tree rings from a drought-prone site show δ¹³C becoming less negative over a period. The most likely physiological interpretation is:
C. Higher intrinsic WUE through tighter stomatal control
Less discrimination against ¹³C occurs when internal CO₂ is lower relative to ambient, usually through stomatal limitation, indicating higher A/gs.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Using Q₁₀ = 2, what is a respiration rate of 2.0 µmol m⁻² s⁻¹ at 15 °C when temperature rises to 20 °C?
C. 2.83 µmol m⁻² s⁻¹
2.0 × 2^(5/10) = 2.0 × 1.414 = 2.83. 3.00 assumes half of a doubling is linear; 4.00 is the 10 °C value.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Green leaves contain 2.0% N and freshly fallen leaves 0.9% N (on a comparable basis). What is the N resorption efficiency?
D. 55%
(2.0 − 0.9)/2.0 × 100 = 55%. 45% is the fraction remaining in litter; 1.1 is the difference in percentage points.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
In determinate (preformed) shoot growth, the leaves of next year's shoot are:
A. Formed in the bud during the previous season
Preformed shoots expand in one spring flush; indeterminate shoots continue to form leaves during the season.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Growth inhibition of a bud that cannot be overcome by favourable conditions until a chilling requirement is met is called:
C. Endodormancy
Lang's endodormancy is internal to the bud; ecodormancy (quiescence) is imposed by environment; paradormancy by other organs.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Suppression of lateral buds by the terminal bud in the same shoot is an example of:
B. Paradormancy
Inhibition by another organ (apical dominance) is paradormancy.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Tree-ring studies worldwide show a rise in intrinsic water-use efficiency with rising CO₂. What have they generally found for growth?
B. Little matching growth gain
Higher iWUE has often not translated into faster growth, suggesting nutrients, drought or warming limit responses.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
Atmospheric CO₂ was about 280 ppm before industrialisation. Roughly what level had it reached by the mid-2020s?
D. Over 420 ppm
Global mean concentration passed 420 ppm in the early 2020s.
Further reading: See the manual sources: Pallardy, Physiology of Woody Plants; Tyree and Zimmermann; Lambers et al.; Smith and Read; Hartmann and Kester
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