Canopy photosynthesis, evapotranspiration, leaf nitrogen, and transcription profiles of maize in response to CO2 enrichment

Soo-Hyung Kim, Richard C Sicher, Hanhong Bae, Dennis C. Gitz, Jeffrey T Baker, Denis J. Timlin and Vangimalla R. Reddy

What does the title tell you?

Why are there so many authors?

Reading a scientific paper

2

Soil-Plant-Atmosphere Research Chambers

• Enclosure of a plant canopy

• Control– CO2

– Temperature– Relative humidity– Fertigation

• Monitor– Canopy photosynthesis– Canopy evapotranspiration– Canopy temperature– Soil moisture– Root growth

Chambers cost ~$120,000 each and there are 12 in this facility at Beltsville MD.

BIOL424/ESRM478 3

Tubes used for Measuring Root Growth

BIOL424/ESRM478 4

How do scientists read a paper?

Abstract

Discussion

Captions and their headings

Introduction

Parts of the results

Parts of the methods

Three things about this paper:

1. The basic conclusions

2. Are the conclusions justified?

3. The logic of the study

No change in photosynthesis

Increased WUE

1. The basic conclusions

Increased CO2 concentration

No difference in biomass

Decreased Nitrogen uptake

Reduced number of stomata

Reduced transpiration

2. Are the conclusions justified?

Strengths:

They give you an empirical result (no

difference in biomass) and research

reasons why that result was obtained.

They attempt to be broad in scope in

researching the processes. They use

transcription profiling as well as measures

of canopy and leaf photosynthesis.

Some weaknesses

Only three replicates – low power

e.g., page 592

“The number of tillers per plant was 1.52 and 2.06 (P = 0.08) in the ambient and elevated Ca treatments,

respectively.”

Why the major result (enhanced WUE) has no effect on

yield is not really explained.

The microarray data is only a partial representation.

The statistically significant difference in leaf N content 3.0

(elevated) to 3.3% ambient is quite large but its effect is not

explained.

3. The logic of the study

The study is basically confirmatory the results

obtained were all suggested in the introduction.

The major addition is that photosynthesis is

measured continuously using the SPAR chambers.

Some points of explanation

Leaf photosynthesis measurements are often poorly correlated with yieldwhy?

“fertigated”

DAP days after planting

Silking

Feed-forward, feed-back proportional-integral-differential control

Condensate removal humidity measurement

A/Ci and A/Q response determinations

Liquid nitrogen

Bonferroni adjustmenta correction of the level used in statistical testing when multiple comparisons are made.

Regression analysis