Biology-Online • View topic - LDP & SDP's graph

## LDP & SDP's graph

Plants!

Moderator: BioTeam

### LDP & SDP's graph

Hiya,

Could you help me explain this question? I think I attached a graph picture, and the "answer" to go with the graph was: "Critical day length = the day length at which flowering is initiated.
CDL=12h for white mustard (LDP) so needs a photoperiod of more than 12h.
CDL=15h for morning glory (SDP) so it needs a photoperiod of less than 9h
before flowering will be initiated [24h-15h (CDL) =9h], so CDL is really CNL."

Wait... so for a LDP, the photoperiod > Critical day length, whereas for a SDP, the photoperiod < Critical NIGHT length? Shouldn't it still stay < the Critical day length?

*confused* Yes, I have asked my teachers, resulting in a "I don't know why, just do it" and "I can't be stuffed, get a life, and ask me on the week of the test". I know, I know.

Fast Sandslash.
Attachments
Picture of graph
fastsandslash
Garter

Posts: 30
Joined: Fri May 28, 2010 9:11 am

how did you come up with the 9 hours?

CDL=12h for white mustard (LDP) so needs a photoperiod of more than 12h.
CDL=15h for morning glory (SDP) so it needs a photoperiod of less than 9h

this means actually both the same. If something, you would need more than 9h night
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

JackBean
Inland Taipan

Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm

### Re: LDP & SDP's graph

I didn't. I would have thought the photoperiod would be less than 15 hrs. The teachers, said it is actually a photoperiod of 9 hours, because it needs less than 9 hrs photoperiod? Ok... so photoperiod is the length of day for LDP, and photoperiod is length of night for SDP? Really?

Oh well. I'm confused. Hopefully the teachers will be more inclined to answer this week. XDDD
*crosses fingers*
fastsandslash
Garter

Posts: 30
Joined: Fri May 28, 2010 9:11 am

I don't think so. He just probably made it "simplier", as is it shorter...
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

JackBean
Inland Taipan

Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm

### Re: LDP & SDP's graph

Apparently now, the short day plant has a photoperiod of less than 15 hours for the plants to flower. So it is that!! Apparently, it was confusing that the short day plant actually has a long photoperiod, but is considered a short day plant 'cos it flowers when the photoperiod is of that "less" than the critical day length while a long day plant flowers when it is "more" than the critical day length. XDD Happy now ;D
fastsandslash
Garter

Posts: 30
Joined: Fri May 28, 2010 9:11 am

it does not have long photoperiod. Imagine, the day (light) could be long e.g. only 5 hours and it would be fine, but longer than 15 hours would be inhibitory.
On the other hand - long day plants require at least 12 hours, so it can be e.g. 20 hours sunny, but if it's only like 10 hours, it won't flower
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

JackBean
Inland Taipan

Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm