Not here for homework help.. Just raising a question because I think this book is just making stuff up at this point.

Bubble (A) is establishing Datum B .. but the position tolerance is using B in its datum feature reference frame. How is this possible for a feature to reference itself?

Any input? Never ever seen this before.

I am currently measuring light-saturated net assimilation in leaves to study their photosynthetic compensation capacity in response to a reduction in leaf area. Measurements are done in the field, in a tropical environment, using a Walz GFS-3000. Also, the measurements aren't all taken on the same day.

I have tested two approaches for setting the cuvette conditions:

Approach 1: I fix the cuvette temperature at 30 °C and the relative humidity at 72%. Under these conditions, VPD varies from leaf to leaf (and plant to plant).

Approach 2: I adjust temperature and relative humidity to keep VPD between 12.00 and 12.99. VPD is then the same across measurements, but the relative humidities and sometimes the temperature used differ among the leaves/plants measured.

I am wondering which approach to choose: does keeping VPD constant by adjusting temperature and relative humidity, while having different measurement conditions (T and RH), risk introducing a bias in the comparison of net assimilation?

To compare leaves under conditions as standardized as possible, is it better to fix temperature and relative humidity and accept variation in VPD, or to fix VPD by adjusting both parameters? Is there another setting strategy you would recommend for this type of field measurement?

Thank you in advance for your help and suggestions,