<PAGE>



                                                             Executed in 6 Parts
                                                           Counterpart No. (   )

                              NATIONAL EQUITY TRUST

                          LOW FIVE PORTFOLIO SERIES 37

                            REFERENCE TRUST AGREEMENT


     This Reference Trust Agreement dated February 14, 2001 among Prudential
Securities Incorporated, as Depositor and The Bank of New York, as Trustee, sets
forth certain provisions in full and incorporates other provisions by reference
to the document entitled "National Equity Trust, Trust Indenture and Agreement"
(the "Basic Agreement") dated February 2, 2000. Such provisions as are set forth
in full herein and such provisions as are incorporated by reference constitute a
single instrument (the "Indenture").

                                WITNESSETH THAT:
                                ---------------


     In consideration of the premises and of the mutual agreements herein
contained, the Depositor and the Trustee agree as follows:

                                     Part I.
                                     ------


                     STANDARD TERMS AND CONDITIONS OF TRUST


     Subject to the provisions of Part II hereof, all the provisions contained
in the Basic Agreement are herein incorporated by reference in their entirety
and shall be deemed to be a part of this instrument as fully and to the same
extent as though said provisions had been set forth in full in this instrument.

A.   Article III, entitled "Administration of Trust," shall be amended as
     follows:

     (i)  Section 3.14 Deferred Sales Charge shall be amended to add the
          following sentences at the end thereof:

<PAGE>

                                      -2-

                "References to Deferred Sales Charge in this Trust Indenture and
                Agreement shall include any Creation and Development Fee
                indicated in the prospectus for a Trust. The Creation and
                Development Fee shall be payable on each date so designated and
                in an amount determined as specified in the prospectus for a
                Trust."

                                    Part II.
                                    -------


                      SPECIAL TERMS AND CONDITIONS OF TRUST


The following special terms and conditions are hereby agreed to:

A.   The Trust is denominated National Equity Trust, Low Five Portfolio Series
     37.

B.   The Units of the Trust shall be subject to a deferred sales charge.

C.   The publicly traded stocks listed in Schedule A hereto are those which,
     subject to the terms of this Indenture, have been or are to be deposited in
     Trust under this Indenture as of the date hereof.

D.   The term "Depositor" shall mean Prudential Securities Incorporated.

E.   The aggregate number of Units referred to in Sections 2.03 and 9.01 of the
     Basic Agreement is 125,000 as of the date hereof.

F.   A Unit of the Trust is hereby declared initially equal to 1/125,000th of
     the Trust.

G.   The term "First Settlement Date" shall mean February 21, 2001.

H.   The terms "Computation Day" and "Record Date" shall mean on the tenth day
     of May 2001, August 2001, November 2001, and February 2002.

I.   The term "Distribution  Date" shall be on such mean on the twenty-fifth
     day of May 2001, August 2001, November 2001, and February 2002.



<PAGE>

                                      -3-


J.   The term "Termination Date" shall mean March 14, 2002.

K.   The Trustee's Annual Fee shall be $0.90 (per 1,000 Units) for 49,999,999
     and below units outstanding $0.84 (per 1,000 Units) on the next 50,000,000
     Units, $0.78 (per 1,000 Units) on the next 100,000,000 Units, and $0.66
     (per 1,000 Units) on Units in excess of 200,000,000 Units. In calculating
     the Trustee's annual fee, the fee applicable to the number of units
     outstanding shall apply to all units outstanding.

L.   The Depositor's Portfolio supervisory service fee shall be $0.25 per 1,000
     Units.

               [Signatures and acknowledgments on separate pages]

<PAGE>

                                      -4-

The Schedule of Portfolio Securities in Part A of the prospectus included in
this Registration Statement for National Equity Trust, Low Five Portfolio Series
37 is hereby incorporated by reference herein as Schedule A hereto.